For those of you who don't know what an OS-tan is, it's a personification of a computer operating system (expanded to computer applications, such as Firefox, and game consoles too, but they're not so much "official" OS-tans) that started with good old Futaba Channel (and if you don't know that, well... wiki? xD). They had precursors, but the widespread OS-tans most people know (if they know them) pretty much began on Futaba. Usually they're made into women, thus the -tan suffix (a cute version of -chan), but there are male versions of most OS-tans as well, called OS-kun. The Windows girls are usually kinda like sisters and have a rivalry with the Mac girls, but not all of them fight.
So, anyway, I love OS-tans. My favorite (as evidenced by my avatar, I'm sure xD) is 2k-tan. I love robo-girls with blue hair and glasses! And 2k-kun is sexy, too- nothing I like better than a guy with glasses in a suuuuuit >w<. In the comics I find 2k-tan hilarious; she tries so hard and is probably the most competent of the Windows sisters, but then she's got the rest of them to deal with
. I like them all, though. It'll be interesting to see how much Vista-tan/Vistan surfaces, as people doing OS-tan art is more widespread than it was. If I had to note a trend in Vista-tan personification I'd say a teenage girl with pigtails (I've seen her hair green a few times, and blonde a few times, but again there are a lot of different ones) and usually in goth-loli of some sort, but I've seen a lot of different ones. A forehead gem is another thing I've seen on lots of Vistans. Some of them literally have horns because of the whole Longhorn thing, but most of them seem to interpret that as pigtails or ponytail.
Not sure she even exists... but she would be the only one that would be truly cute... I mean... a winows-whatever-version-tan... no matter how cute she is, i would just use her as a vodoo-doll every time my computer crashes 
