Notes

OS-tans are a subset of personifcations of various computer programs, which, in this case, are operating systems.
Most often, they are Microsoft Windows operating systems in particular.
It started as a micromovement of ameteur artists on 2chan, although Microsoft has officially used the idea, as well.
Since early OS-tan designs were unoffical, and not worked on as a team, there would be multiple different designs which arose whenever a new edition of Windows was released.

The term "OS-tan" refers to 'Operating System', followed by '-tan', an honourific similar to -chan, used often nowadays for mascots in Japan.

Based off of search interest, they peaked in popularity in 2004, and haven't had much of a presence since.


Personification

People have been personifying things for thousands of years.

Even before the OS-tan movement started, there were already works containing computer programs being depicted as people,
such as this artwork of the iMac from 1998.
Note that this page mispells "tangerine" as "tangeline".


2chan OS-tans

The first OS-tans were a part of a concept manga knows as Trouble Windows, which had the general plotline of operating sytems acting as maids for their owner.
A creation related to this idea was a Trouble Windows OP, titled 'Troubled Windows', for a theoretical anime adaptation of this theoretical manga.
A higher quality version of the opening can be found here.
Some uploads simply title it as "Trouble Windows", without the "d"; I suspect that the correct nomenclature is that 'Trouble Windows' is the title of the story, while 'Troubled Windows' is the name of the song in the opening.
There also exists a supposed ED created in the same style, though the original upload of it has been removed from Youtube.
It may be this video, but I can't find much information about this one, and it may just be an alternate OP, instead.
I found this video as well, based off of Futari no Mojipittan. I think it would fit the roll of an anime ED just fine.
There are quite a few other videos from this era, as well:

An element related to the characters designs and personalities is the RAM requirements of the tan's respective OS.
Sometimes, this is attributed to the breast size of the OS-tan; due to varying artstyles and character designs, however, this is not consistent.
It is also sometimes related to the apetite of the OS, with more 'RAM-hungry' tans being depicted as eating more often.

During this period, a group of 25 artists got together to create one book about the OS-tans, titled 'Trouble Windows OS-tan Fan Book'.
It was published by Ohzora Publishing on , and sold for 2,205 yen, as seen on their website.
It's still listed on their current site today, although most distributors don't seem to carry it.
Included in the box are 3 figures made by Furoku:

As for the figures, the names of the OS-tans are not simply '-tan', such as 'XP-tan', but are rather refered to as 'OS Girls' (somewhere. The current site just gives them their usual names).
So, for example, XP-tan's name is 'OS girl XP'.

The display for the figures also has a fourth space, fit for a 2k-tan figure, which was sold separately for 800 yen.

I found a review of the figures.
The review states that the quality of the figures, specifically the paint job, was underwhelming.
The writer also compares them to other OS-tan figures, released by Pink Company.

History of the Operating Systems

During the 1990s, Windows OSs were running on a codebase known as '9x'.
As time progressed, however, Microsoft was attempting to integrate a new codebase to suit more modern PCs.
This new codebase was known as Windows NT.

In the year 2000, Microsoft was planning to release 2 different versions of Windows: one for businesses, and one for home users.
The business version, Windows 2000, was released at the start of the year, and ran on NT: the base edition of which was the Professional edition.
It was received well, and ran better than many previous versions of Windows.

Originally, the home release which was planned, known as "Windows Neptune" at the time, was merged with other projects, leading Microsoft to rush to release a different OS to fill its role instead.
This new home version, Windows ME, was released closer to the end of the year, and was still using 9x.
As such, ME ran poorly on the hardware of the time, and was incompatible with much of the recent software, as well.
Additionally, since it did not include the ability to run DOS-based programs, it could not run much of the older software, either.
Because of this, it was prone to crashing and bluescreening often, and its instability lead many to consider it to be one of the worst operating system releases of all time.

The merged Windows Neptune would become the basis for Windows XP, which was released a year later in 2001, made many changes to the layout of Windows, and could run both 9x and NT code.

It is this relationship between the reliable 2000 Professional edition, the unstable Millenium Edition, and the new and experimental XP which lead to the creation of the three main OS-tans.

Left: ME-tan, Middle: XP-tan, Right: 2k-tan

ME-tan -Millenium Edition-

The OS-tan which first popularized the movement was ME-tan, which personified the Windows Millenium Edition's numerous issues, such as often crashes, by moulding them into personality traits applied to an anime girl.
As an operating system, her role is to perform all of the tasks requested of her by the PC's user.
In this respect, however, due to Millenium Edition's multitude of issues, ME-tan is unable to do her job correctly.
As such, she is characterized as a young girl with a goofy personality, she's a total clutz, and her main personality traits are foolishness, a lack of sense, and unreasonability, usually played for comedic effect.
Due to her incompetence, she often causes more problems than she solves, which in turn have to be resolved by the other, more mature OS-tans.
Still, she always tries her best.

Her OS-tan Collections page says that her creator is "now called ME-aki",
although I have yet to find any trace of this person online as of yet.
It also says that she is often known as "Emui-san", although I have yet to see many sources use this.
I will sometimes, though.
Note furthermore that this page refers to NT-tan as ME-tan's step-sister, and also that NT-tan is the mother of 2k-tan and XP-tan.
Considering the release history of Windows, and that ME is a 9x-based OS, this makes sense.
It does, however, present an odd family dynamic, since ME-tan would be looking up to her nieces as parental figures.

As for her design, to resemble the logo for Windows ME, which has a green box around the Windows logo, along we typically green text, she has green hair.
She wears a dress similar to that of a maid, as her job is to serve the device's user (sometimes referred to as a 'master), with jobs such as 'cleaning' file directories, and making sure that the PC is virus-free.
Around her neck is a bow or cravat of some sort with an exclamation point inside of a triangle.
This symbol is supposed to parallel the error icon, since the OS was especially prone to error messages.

Since ME-tan was the OS-tan which first caused the movement to gain traction, her design is that which is most unanimously agreed upon.
Aside from her green hair and eyes, her dress is blue, and she wears various red ribbons; the two other colours prominent in the Millenium Edition logo.
Aside from colours, there is also her her style.
She has usually two, although sometimes only a single, braided tail.
She is also drawn with an ahoge of varying sizes, usually very large (she can use it to fly; it works like a propeller).
This makes sense.
After all, everone knows that, as the ahoge size increases, so too does the brain size reciprocally decrease.

ME-tan often wields an onion stick as a weapon.
This is supposedly a reference to an anti-virus program which was popular in Japan at the time, known as NeGIs (which I can only assume was spelt ネギス, Negisu).
So, to fight of malware attacks, she uses NeGIs (note that I can't find any other information regarding NeGIs, or that it was even a thing).
To understand the pun, note that the word for that type of onion in japanese is ねぎ (Negi), which is hiragana analagous to ネギ (Negi).

A further expansion of this concept is to instead have ME wield a crowbar.
This most likely started since the two objects look similar when drawn in black and white, so I imagine that they were often confused for one another.
Additionally, as anyone who has played a source game would know, crowbars are the height of humorous weapons, so it's a natural fit for a comedic relief character to wield one.

ME-tan is usually depicted as the foolish-yet-hard-working young girl comedic relief archetype you may find in something like Azumanga Daioh or Yotsuba&.
As such, another popular genre of funny spinoff images is that of an extremely muscular or violent Emui.

2k-tan -2000 Professional-

The OS-tan for Windows 2000, specifically the Professional edition.

At the time of its release in , Windows 2000 was considered to be the most effecient and stable operating system which Microsoft had released.
To reflect this, 2k-tan was given a 'mature servant'-like personality, which translates into her being the parental/guardian figure for ME-tan, as well.
Among the other OS-tans which were present at the time, she is usually depicted as the 'sensible adult' of the group.

As for her design, to present her sophisticated apearance, she is usually drawn with European maid-style clothing.
The most common element of this depiction is a maid's hairband, which she is almost always drawn with.
She often wears a blue dress or overcoat, as well, which has a long skirt which emulates that of a maid's dress, and a bow, tie, cravat, or ribbon of some sort.
Some art, however, has her wearing a suit, instead.
Her most common design also wears a one-piece apparel with the four colours of the Windows logo, which is often described as a "swimsuit".
I see no reason why this has to be the case, however, since there are plenty of non-swimsuit clothes with that model,
and I have yet to once see art of her swimming in said swimsuit.

Other common elements of her design are her blue hair and blue eyes --blue which is supposed to be that of the Windows 2000 default colour scheme,-- along with glasses (because anybody who wears glasses is obviously smart).
Along side her hairband are two objects, often mechanical in nature, which are supposed to represent cat ears.
The is due to her name, にけ (Ni Ke, or 2k), being close in spelling to にゃけ (Nya Ke), with にゃあ (Nyaa) being the sound which is attributed to cats in Japanese.

This relation to cats comprises one of her alternate characterizations, with a more playful personality, similar to that of a cat.
Art of this kind often has her with organic cat ears, and a tail as well.

A third aspect which is usually attributed to 2k-tan is her affinity for weapons and combat in general.
This includes her being drawn with guns, swords, mecha suits, and other, usually high-tech weapons.
This is most likely due to her design being reminiscent of various Mecha Musume series, with her maid clothes and machine cat ears and such.
Coincidentally, computer viruses were especially prevalent around the time of Windows 2000's release, so it makes since that she would have to do a lot of fighting.
As the guardian of the group, she would also have to protect the other OS-tans, as well.

XP-tan -Windows XP-

The OS-tan for Windows XP.
When the OS-tan movement first started, XP was the most recent Microsoft operating System.
The keys 'x' and 'p' on Japanese keyboards are also the keys for 'さ' (sa) and 'せ' (se) respectively, so she is often nicknamed させこ (Saseko).
Around the time of its release, XP made many changes to structure and UI of Windows, and, along with other changes, caused it to have quite a few critics upon its release, especially on Futaba.
The main gripes people had were the amount of unnessecary programs and features, often called 'bloatware', and the overhauled UI and menus were at first too flashy and over-designed for some people.
It also demanded more RAM usage than previous operating systems.

For these reasons, XP-tan was first known for promiscuity and having a shallow personality. The OS-tan Collections page goes as far as to describe her as a "shallow piece of bloated eye candy".
Furthermore, due to her tendancy to 'eat' RAM more than previous versions of Windows, XP was known as a 'gluttonous' system.
To reflect this, her other main trait is eating, usually rice.

This characterization was due to how XP was first perceived, but it did not remain that way forever.
Not only due to the operating system's popularity, but also because it has since been compared to more recent, less respected operating systems, XP became a strong contender for the title of 'Microsoft's best OS'.
Since people didn't maintain the stigma held for her when XP first launched, Saseko isn't seen as having the negative personality traits she was first created with.
She's also particularly popular in the west, at least when compared to the other Futaba OS-chans, likely because early reception of XP wasn't as dogmatic when compared to Japan.
Still, she maintains her design which reflected her original promiscuous personality, and she's still shown to eat a lot.

Her design usually has her with dark hair, varying between brown, black, or dark blue, with either one or two "XP" hair clips.
She usually wears her hair down, although there are quite a few works with it in a ponytail.
As a part of her original interperetation, she usually wears skimpy clothes, either short or tight in nature.
She often wears clothes made with transparent or see-through material, most often her sleeves around her arms (that, or she is very, very damp).
Some art has her wearing clothes styled after a seifuku, as well.
The most common element between all of these outfits is the short skirt, which contrasts the longer skirts or coat-tails of the maid-styled OS-tans.
Another common element, and I mean really common, is a golden ring around her neck, with two red ribbons hanging off of it.
It's in almost every single drawing of her, no matter which artist drew it, or whatever alternate outfit she's wearing.
I have absolutely no clue what it's called or what it's supposed to represent.
Aside from the clothes, the 'RAM-requirements-are-equal-to-breast-size' belief about OS-tan designs is likely in reference to Saseko in particular, since she is usually drawn weller-endowed that the other OS-tans.
She often fits the role of fanservice character, in both design and role, in most webcomics, especially older ones.
Pantsu gags are very prominent (see: notes on the short skirt).

XP-tan aligns with the role of OS-tans, which are servants who perform the roles of the OS they represent, even though her design does not match the maid-style of the other OS-tans.
To accomplish this, she is often seen showing a closer attachment to the user, such as that of a housewife, I suppose.
In her original depiction, this was due to her desire for attention being used as a negative trait.
Now, though, this close relationship is considered to be a positive trait.

A "popular" alternate rendition of XP-tan is for the home edition of Windows XP, suggesting that Saseko is the professional version of XP.
I say "popular", but I haven't been able to find much art of her.
Her name is Homeko, and the main aspect of her design is her green ponytail.
She supposed shows up as a fujo lot in fanfiction, although I haven't found much of that yet, nor do I intend to read much of it, either.

I usually try include a section about weapons at some point in these articles...
XP-tan, however, is not exactly depicted in combat often.
Here's a picture of her with guns, at least:

95-tan -Windows 95-

The OS-tan for Windows 95.
Aside from the trio of the main three OS-tans, 95-tan seems to be the runner-up in terms of popularity, putting her in fourth place.
She appears in most group fanart, though the number of individual fanart of her is slightly lower than ME-tan, 2k-tan, or XP-tan.
Unlike the other three, I have yet to find a common nickname for 95-tan which has a sensical meaning.
Since Windows 95 was the first OS to use 32-bit operating, which became the standard by the time of the first boom of OS-tan art, she has a noticeably historic design.

To match the servant trait of the other OS-tans, 95-tan is usually drawn doing things which were common tasks of servants and maidens during older era of Japan.
These tasks include cooking and brewing tea, notably with historical equiment and comportment (I think; I'm not a 100+ year-old Japanese person).
Although her design is supposed to reminisce of a much older time period than the other OS-tans, she doesn't seem to be much older than say, 2k-tan, for example.
Her wikipedia entry suggests that she is unfamilar with recent technology, though i have yet to see much art depicting her in such a fashion.

Her hair is long, either brown, rose, or burgundy.
Somtimes it down, while other times, it is in a ponytail.
Her most unanimous element is her hair ribbon, which has the one of the four colours of the Windows logo on eack of its tails.
Quite a few artists like to draw her with small, round glasses.
Her clothes are those which were popular among Japanese women near the start of the 20th century, such as during the Meiji era, for example.
These include a kimono, obi, hakama, and geta in the style which was à-la-mode during the late 19th century.
The numbers '95' are often stitched into her obi, which I'm fairly certain is that belt which ties around the kimono.

Her kimono's material is based off of one of the backgrounds for Windows 95 in Japan, known as '花見.bmp', which most OS-tan websites just refer to as 'hana256.bmp'.
Searching for 'hana256' yields very few search results, which made finding the image difficult to locate.
Rest assured, though, it does exist:

花見.bmp, otherwise known as 'hana256.bmp'

The only source I'm aware of which actually links the image to the name 'hana256' is this Twitter post from 2021.
The OS-tan pages which reference eachother for information, however, haven't been changed much since the mid-2000s.
I suppose the origin of the name 'hana256' will be a mystery for some while longer.

As is common with characters who wear the fashion that she does, 95-tan wields a katana.
She is sometimes shown with other historical Japanese weapons, as well, but the katana is the most common.
There is lots of art with her and her sword, even more than 2k-tan with her weapons.
It reminds me a lot of the character designs in things such as Ruroni Kenshin or Sakura Taisen.

Vis-tan -Vista-

With the release of Windows Vista, there was an all-time high of artists trying to create the generally accepted design for the next Microsoft OS.
Ironically, because of this, there are many designs for Vis-tan which gained quite a bit of traction.
Unlike other operating systems, there is no widely accepted agreeance for what Vis-tan should look like.

Her section on the wikipedia article is written from some sort of a recent present tense (I'm not an English major),
which makes it sound like it was written around the time that windows Vista was first released, and people were creating all of her different designs.


Official OS-tans

The major difference between the old OS-tans and Microsoft's OS-tans are that Microsoft never refers to their mascots as 'OS-tans', at least in all of the promotional material I've seen so far.
These girls are fundamentally different than the older OS-tans in that they aren't really implied to be the operating systems themselves.
Nanami, for example, is shown to build a computer and run Windows 7, which she herself advertises.
ME-tan, on the other side of the coin, is the very concept of Windows Millenium Edition personified.

Madobe Nanami

Nanami is the Windows 7 OS-tan appearing in official Microsoft promotional material, including this video.

Nanami's quite the genki girl, judging by her dialogue in the commercial.
She seems to be rather forgetful, as well.

If you want to listen to the song from the commercial, it was sung by her VA, Nana Mizuki (what a coincidence), and released under Nanami's name.
Its title is 'Seven Color Generator'.

Madobe Yuu and Madobe Ai

The OS-tan sisters for Windows 8.

Their names are both a pun of "You & I", as that is what they are often refered to as in files, as well as "UI", since a major change in Windows 8 was its UI compared to previous Windows versions.

Most official material regarding the Madobe family states that they are twins, with Yuu being the elder of the two; although the Wikipedia page state that there seems to be material which somehow conflicts with this, I have yet to find what that is in reference to.

One of the sisters has longer hair, and wears a serious expression, whilst the other has shorter hair and is usually depicted with a smile.
The girl with long hair is Ai, while the shorter-haired one is Yuu.
Note that I haven't seen anything that states this directly yet, but the way the the names are positioned in promotional material would suggest that this is the case.

Windows 8 was deisgned for use with both Windows Tablets and Windows Phones that Microsoft was manufacturing at the time; as such, the two sisters are supposed to represent the mobile and PC dichotomy of the OS.
Since Ai (the longer haired one) is often seen holding a tablet, I think that it's safe to believe that she's supposed to be the mobile aspect, while Yuu is the PC aspect.
Then again, sometimes the roles are swapped, so it may just be a coincidence.

Like Nanami, the twins also released music; this time, two songs.
One is known as Mir8cle Days.
The other is known as Donna Mirai Demo, of which I just happened to be the person to upload it ( :) ).

Launch of Windows 8

When Windows 8 first launched in Japan on , there was a release event held in Akihabara.
Sold at this event were promotional material related to Yuu and Ai.
Among the merchandise were 2 versions of theme packs for Windows 8, which included a custom mouse, as well as both voicelines and 4 background images (three wallpapers and one picure password image) featuring the OS-tan of the version which was purchased; Windows 8 was packaged in, as well.
These were sold for 18,000 yen.
The diffence between the two versions were the voicelines for Windows SFX, which were more prominently stated by one or the other of the sisters, as well as one unique background image, along with a unique picture password image.
There were 4000 released for the Yuu edition, and another 4000 released for the Ai edition.
The box of this release was a plain white.
While both sisters appeared on the packaging of the box, to denominate which girl the version was for, said girl was larger, and placed more prominantly on the center of the box.
The official page detailing this campaign is accessable via the Wayback Machine.

A special edition was also sold, with 444 copies for each girl.
Due to pre-orders, this version was reportedly sold out almost immediately.
The box of this release was a reflective gold.
This version, as explained here, contains different unique images than those contained in the more common release.

There was even a third edition, with 500 copies per sister, sold from around 18,000 yen to 20,000 yen.
It was available only in Osaka Nihonbashi, and contains different unique images than both of the other two versions.
The box for this one had a leopard print(!?) With a blue stripe on top.
On the top left of the front of the box was a sticker which showed which sister was contained within; the orange sticker was Yuu, while the magenta sticker was for Ai.
The release of this edition was specifically for people who were unable to attend the release event at Akihabara, and pre-ordering this version forbayed you from participating in the event.
I'm not sure how they enforced that last point.

From the sales of these editions, it's possible to conclude that one of the sisters was more popular than the other, as concluded by this Japanese article.
However, the translation is nebulous in this regard, as it states that, after the first day of sales, "we heard many people say that the stock of the Ai Window Edition was smaller than that of the Yuu Window Edition."
Whether that refers to the stock sold or the stock remaining is something I have yet to uncover.

This campaign was rather successful, it appears, as the launch sales of Windows 8 were far greater than those of Windows 7.

Madobe Claudia

Claudia advertises Microsoft Azure.
That's not exactly an OS, so is she still an OS-tan?
I don't know what to call her.
Her name, Claudia, is in reference to the fact that Microsoft Azure is a cloud platform.
She is supposed to have a webcomic, possibly stored somewhere on the Japanese Microsoft site, but I have yet to find it.

Some of Claudia's webcomic can be found via the Wayback Machine, although only some of the images were saved.

Aizawa Inori

The tan for for Internet Explorer.
She makes her debut in this advertisement, where she fights some robots.
It was first shown at an anime festival, Anime Festival Asia 2013.
She seems suited for combat. Are all the OS-tans this strong?

Internet explorer is no longer supported, could something like this be made for Microsoft's new browser?

I guess you could say she stood a little too close to the Edge.

Aizawa Hikaru

Hikaru was used by Microsoft's Taiwan division in material for Microsoft Silverlight.
There was once a video of her on the Taiwanese Microsoft site, but it is no longer there.

If you cannot tell yet, the offical Microsoft-tans are related to eachother via family.
You can find a family tree on the Japanese page for Nanami.

Others

Some promotional material has various other, usually nameless, tans.
This page notes one such tan for Microsoft Virtualization.