bad topic for a poll simply b/c so many use different OS's. I have 2kpro, xppro, mandrake and freebsd on my several machines, some single boot, some multi-boot. *shrug* not very interesting really

edit: re: 2k is a screw up...
i'm not sure what you're talking about. maybe you're thinking of me (which is definitely a screwup). 2k is actually a hell of a lot more stable for me than xp is. If you're running a server of any kind, you'd definitely want to use 2k over xp or me (unless you're rich and can afford 2k3). It's a solid OS (though i have seen it BSOD plenty, but then I do some ridiculous stuff with my computer sometimes. . )