check your cpu temp. and also do a virus and adware scan. mine did that to, then i reformatted the hdd and it fixed it.
konny
my computer randomly reboots. it happens most often when i am playing a game, but can happen at anytime. sometimes it will reboot in 5 minutes or other times after a couple hours. i have read other posts on other sites about this and have tried many things. i switched video cards with another computer, but it still restarts. i reinstalled windows xp and it still does. i have read on another post to uncheck the automatically restart box under system failure. a bsod shows up but says nothing.it is just a blue screen. i don't know what else can be the problem. any advice would help.

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic