I have a quite new computer (P4, 2000 MHZ, win XP) but lately, it restarts randomly whenever it feels like it...
sometimes it happens even a minute after it restarted (before windowes is fully up) so i don't think it's a software problem, and also, if i keep the computer off for a few hours, it can work for a long time without restarting itself, but once it restarts, even if i try to work it again, it'll restart again in a few mintues...

does anybody have a clue for what might be causing this? overheating? power supplier? aliens?