Been having a problem with my computer video randomly freezing or my computer rebooting, while playing 3d games.

All other apps seem to run flawlessly. Don't normally receive a BSOD, though I did get one last night that said : bug_code_usb

The usual is that the video stops responding and the computer completely freezes. The screen still displays the frozen image, but the computer becomes unresponsive, I'm then forced to do a hard reboot. The other common occurance is the computer just goes straight to POST (normally upon launching a game).

I've tried a few different video cards over the past few days. ATI cards do not seem to work in the system at all, computer will not get past POST with an ATI card installed. Fails after POST and before Windows loads.

Nvidia GeForce 6800 GT OC will run ok, but I'll get random freezes while gaming.

Each time I load a new video card, I first remove the old drivers and then install the drivers for the new card after I've installed the card.

I have gone though and made sure the computer is as dust free as possible and have re-seated the video card, memory, and cpu.

I've been tracking the heat from the CPU and the Video Card, they are both well in the "green" and I'm not getting any kind of heat warning though the system temp monitor.

System Specs:

AMD Athlon 2500+
MSI K7N2 Delta2 Mainboard with nForce2 drivers
Nvidia GeForce 6800 GT OC: 256 GDDR3 AGP 8x
1.8 GB PC2700
450W PSU
48x CD-ROM
48x/16x CD-RW

I've attempted using different settings in the BIOS for AGP, system seems most stable with it set at 256 AGP apature; FastWrite - Disabled; AGP 8x -enabled; Video RAM cacheable - Disabled. But I'm still experiencing the hangs, about 1 an hour.

I've tested each RAM stick individually, and I've run a DXdiag on the system, it passes all tests.

I've run chkdsk on my system with repair enabled and have no errors on the disk.

Any assistance would be extremely helpful as I think I've just about exhausted my troublshooting abilities. Please let me know if you need any additional information from me, I'll provide it as soon as I am able.

Thanks in advance,

Uunder