Crashing problems while playing games

[Funktion]

I purchased a PC about a year ago, and since the very beginning I've been unable to play games in it, because after a few minutes the aplication crashes.

My first problems started with VISTA 64 Ultimate (the OS that came with my PC), which I soon gave up using because I couldn't even update the anti-virus without the OS crashing, it was highly unstable.
With Windows XP I don't have any major problems in most tasks, but it's been pretty much impossible to play games.

What happens is after a few moments (usually between 1-5 minutes) any game I try to play crashes to desktop. Most error messages point me to either a problem with the driver from my graphics card (8800 GT) or my audio "card" (I don't use a standalone audio card, I use my motherboard ASUS P5KR). Since I already used several combinations, including the updated drivers for both, I really don't know what else to do.

I already formatted and re-installed everything several times, both using the drivers that came in the CDs included with the components, and also with the updated drivers for every component.
I tested my PC's RAM, and no problems were detected. I checked the power source and temperature, and no problems were detected. I asked a friend of mine who works in hardware troubleshooting, and like me he didn't detect any hardware problems, and says it's a driver problem, but he wasn't able to fix it either.


My PC has the following:
Motherboard: ASUS P5KR
CPU: Intel Core 2 Quad Q6600 - 2.40GHz
4GB RAM
GPU: ASUS 8800GT 512MB
2 500GB disks

I've included the DxDiag file from my system.

Any help is appriciated. Thanks

 

[Deathmaker]

Do any of the games that crash have the option to start in safe mode? If they do, try disabling all but the sound & see how it goes. Failing that, disable the onboard sound in the BIOS and see if this makes any difference.

To me, seeing as you've tried a combination of different OS'es and drivers, it seems more likely to be a hardware issue rather than software, particularly a PSU problem. Do you know the make and model?

 

[Funktion]

Thanks for your reply.
I did try to disable sound several times, and while it seems it took a while longer to crash to the desktop, it crashed anyway.
Regarding the PSU, if it was a problem with it wouldn't the OS crash and restart? What happens to me is the applications crash to the desktop, the OS doesn't restart.