What OS do you use?

Mac? Linux? Vista? Windows 7? XP ?

windows 7

Windows XP Professional, dual-booting Ubuntu.

I use Windows Vista and I've been using it for about 2 and a half years now. ;)

Vista 64-bit.

Dual booting Windows 7 Pro 64-bit with Kubuntu 10.10 x86_64

I am running Windows 7 at the moment, only recently upgraded to it though and I am liking it so far.

Mac Os X Snow Leopard.

XP, but I don't really have much of a choice, seeing as I don't technically own the computers, my parents just don't mind me using them as long as I don't install malicious software and such. The other computer I use does have Vista, but I can't stand it... Vista is a pain in the rear.

Windows XP Professional