Probably your RAM is at fault. Did you check your RAM for errors. There is Windows Memory Diagnosis tool inbuilt in windows. check through that for errors
so i built this computer about 2 years ago and all of a sudden my computer is restarting itself at random times. Once it has restarted one time its on some kind of loop. The computer restarts itself untill it is unplugged. I am unable to turn the computer off so thats why i unplug it. The computer was able to be overclocked when i first got it. i havent tried it recently however. I dont know what to check to see what makes my computer restart

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic