First of all, I put this topic to hardware forum because this happens with every game. So, usually after an hour, some pixels on the screen go unclear, sounds stop and the screen just freezes completely. Then I just shut the computer from the power button. This happens only while playing games full screen.
This started after my old video driver broke and I bought a new one, Nvidia Geforce 8500 GT. I have tried formating my hard drive and install new drivers and older drivers but nothing works. I cleaned the dust inside the machine and tested the temperatures and they were ok. Still keeps freezing after about 1h of gaming.
I had this one instance where the computer rebooted itself after the freeze and back in windows the error said that I had a "stop problem" or something and it can be fixed by downloading the newest drivers. Didn't work.
Please help if you have any idea of what this problem might be. My friend told me it might be the power supply but he wasn't sure.