http://static.tvtropes.org/pmwiki/pub/images/ostans_2267.jpg

The OS-tan (short for Operating System-tan) is a MoeAnthropomorphism of various Windows operating systems (or at least that's how it started out), and is now a common feature on the Japanese Futaba Channel (where they originated). In fact, web browsers, antivirus programs, and other applications have gotten similiar treatment.

The -tan is a deliberate mistranslation of the -chan suffix, as it's supposed to sound like something said by a small child (hence evoking cuteness)

Originally, the first OS-Tan was Windows ME-tan, who was drawn as a cute {{Idiot Hair}}ed {{Dojikko}} to represent how the actual Windows ME was highly unstable. Afterwards, several more Windows OS-tans were made, and eventually the premise exploded to making {{moe}} versions of almost every OS or popular piece of hardware in existence. The cult popularity of the OS-tan characters led to Microsoft Japan creating Madobe Nanami, [[AscendedMeme an]] ''[[AscendedMeme official]]'' [[AscendedMeme OS-tan]], as a spokesperson for Windows 7.

In fact, this little phenomenon even sparked a fake trailer for an anime series called ''Trouble Windows'', which has also been licensed as a name for artbooks depicting the OS-tans.

Video of the Trouble Windows trailer [[http://www.youtube.com/watch?v=jYlBuAvSzXk here]]

!!Tropes common to the OS-tans are:

* AloofDarkHairedGirl: Windows 2K-tan is often drawn this way, though XP-tan also has this look on occasion.
* AscendedMeme: Windows 7-tan was given an official personification, [[PunnyName Nanami Madobe]]. Windows 8 has TWO of them, named Madobe Ai and Madobe Yuu.
* BigEater: XP-Tan, who often is shown holding up a big rice bowl labeled "Memory".
* BrotherSisterIncest: Homeko [XP Home Edition] has a crush on her SpearCounterpart brother "Homeo".
* CanonForeigner: Windows 1.0, 2.0, and 3.2 (Chinese 3.1) -tan are regarded as this in fan works.
* CatGirl: Windows 2000-tan's hair clips make her look like one.
** The latest MacOS-tan's are all {{Cat Girl}}s due to their production codenames.
* DepravedBisexual: Dr. Norton [Antivirus] is drawn as an ugly perverted ghost [after the Norton Ghost program] who keeps trying to ogle the Windows-tans at every opportunity, with XP-tan being his preferred victim. He also has an implied fetish for Bill Gates.
* {{Dojikko}}: ME-tan, representing how the system was liable to crash.
* ElegantGothicLolita: How Windows 3.1-tan is often drawn.
* CuteKitten: Windows 3.1-tan is always depicted holding a cute black kitten labeled "DOS".
* HairDecorations: Nearly all the -tans have hair accessories, usually a cute stylized version of the logo of what they represent.
* FanGirl: Windows CE-tan is a big InUniverse fan girl of the Dreamcast, as a variant on the CE OS code was used as the Dreamcast BIOS.
* FieryRedhead: Windows 95-tan when mad.
* FurryFandom (What the web browser Firefox and its companion email client Thunderbird are designed after)
* GirlWithPsychoWeapon (SE-tan and her can opener, wielded with intent to castrate)
* HumongousMecha (Windows 98 and 98SE-tan commonly ride around in ones that resemble snack boxes)
* HospitalHottie (Miss Mc Afee [Antivirus] and AVG [Antivirus], who are both drawn as attractive, with the former being drawn as a monocled British woman and the latter as a good looking male student doctor)
* ImprobableWeaponUser: ME-tan often uses a leek for self defense. SE-tan uses a can opener.
* InstantAwesomeJustAddNinja: Vista-tan has this look as a premise.
* KatanasAreJustBetter: Windows 95-tan's katana represents her dominance over all rival systems of the time.
* LadyOfWar: Windows 95-tan.
* {{Meganekko}}: Windows 2K-tan.
* MoeAnthropomorphism: Usually as a cute girl or woman, though male versions exist.
* PunnyName: Nanami Madobe means [[ExactlyWhatItSaysOnTheTin "Windows 7"]].
** NT-tan (NT 3.1/3.5/4.0) is called Inut-tan, as the pronunciation is very similiar to the Japanese word "Inu", which means dog. In fact, NT-tan is often drawn as a cheerful girl with dog ears)
* SeriousBusiness: Windows 95-tan, in reference to how Windows 95 started off Microsoft's opening shot in its war to outdo Macintosh, gets downright KnightTemplar when it comes to fighting MacOS-tan's.
* ShrinkingViolet: Windows 3.1, DOS-tan and Linux-tan are depicted like this.
* SpearCounterpart: Many OS-tan's originally drawn as girls have male counterparts.
* {{Stripperific}}: Vista-tan, due to the fact her clothes are transparent, in reference to the "Windows Aeroglass" theme.
* StuffBlowingUp: MacOS uses bombs as an attack.
* TeamMom: Windows 95 and 2K-tan assume this role for the Windows OS-tans.
* WhiteHairedPrettyGirl: Windows 3.1-tan and some versions of Vista-tan look like this.
* YaoiFangirl: Homeko-tan.
* YouGottaHaveBlueHair: 98-tan and 2K-tan have blue hair, ME-tan and and 98 SE-tan have green.
* TheWikiRule: Besides having a page on TheOtherWiki, there is an entire [[http://ostan-collections.net/wiki/Main_Page OS Tan Wiki]].
* ZettaiRyouiki: We have XP-tan, 7-tan among others.