Windows XP on my pc but I'll probably buy a new comp once Windows 7 (maybe SP1) comes out pre-installed with it...unfortunately I don't know anyone who can build a custom-made computer. =/
Anyways to the person who posted the win98SE, I like windows 98 too (don't have the 2nd ed. but it works) because it's much more simpler than XP despite it's stable-ness.
IGNs: League of Legends: Allea