I've been experiencing this problem lately...
While working on the PC, everything seems to be OK. However, when I play a game (ex. Warcraft III), I sometimes experience my PC stalling. The display freezes and after a few seconds, the monitor blacks out completely and my PC then automatically restarts.
I was thinking maybe it is due to my video card overheating but when I work on the PC (doing anything besides playing games), I don't experience the problem. Problem arises only when I play a game.
Can anyone help me solve this problem? Thanks a lot.