Windows XP, keeps on restarting

[3dvisioner]

Hope someone can help me. I just recently started getting this problem out of the blue. I have windows xp professional. After long periods of keeping my computer on and idle, it just restarts. It usually happens when I leave my computer on when I'm sleeping, I wake up and see that it's back to the clean desktop and the programs that I was running before are no longer open. It's happened a few times when i was running the program overnet (like kazaa) and downloading stuff. I used to do this all the time but now for some reason my computer is restarting. Has anyone had this problem before and do you know how I can fix it? My full system specs:

windows xp professional
amd athlon xp 1800
512mb ram
mb: gigabyte 7vtxh
ati all in wonder radeon 9700 pro
sound blaster audigy gamer

[iplayguitar]

havent you already posted one like this?

[MrBored]

Yeah, prolly cause no one responded in this forum, its probably that MS blaster worm...