Okay, so the problem is when I try to play certain games, for example Counter Strike Source, Call of Duty 4, Portal, or Unreal Tournament 2004, it runs smoothly for about half an hour, then it freezes up. I can tab out of the game, and then go back in, but it freezes up again within a few minutes, and eventually I get an error that says "Display Driver Stopped Responding." I have a Zotac 8800 GT. Also, I have tried installing the most recent drivers, switching out my ram and resetting the BIOS, none of which worked. If you need more information about my computer specs please let me know. Any help will be greatly appreciated.