VPU recovery errors and lockups (9600XT on Asus K8N)

[Biggles604]

I have built a system on the cheap for a friend, 1024MB Samsung RAM, Asus K8N mainboard, Sapphire 9600XT AGP card, Athlon 3000, IDE 160GB WD drive. I have installed XP Home, all the latest drivers.

The problem: Randomly, the computer will lock up, and it's a 50% chance that the VPU recovery will kick in and save it, sometimes even if the VPU recovery kicks in, the video is garbled and no good, requiring a re-boot. The rest of the time, the screen goes black and a reboot is needed. The problem only occurs when running DirectX games (or benchmarks.) I'm uncertain if it's DX8 or DX 9 processes that are triggering it.
Crashes occur a random amount of time, from 30 seconds to 10 minutes.

What I have tried:
Turned off Fast-writes in BIOS and driver.
Disabled AGP8x support, dropped it back to AGP4x
Re-seated card.
Underclocked card believing it may be heat.
Ran comp with case open and a fan blowing in there.
Took the system back to the store, explaining all this, they installed a new video card thinking that was the problem. It wasn't.

Any ideas?

 

[Rhetoric]

Make sure the fan hasn't died. Turn off VPU recover too in CCC.

 

[Biggles604]

I tried turning off VPU recovery, it made no difference, except, with it on, there is a 50% chance that the game can be saved.

 

[z-lite]

What's a VPU? How about disconnecting/removing anything that's not required such as sound/network card, extra HDs/CD-ROM drive and see if the problem still happens. Maybe it's the PSU that can't supply enough power since the problem seems to kick in with games.

 

[Biggles604]

Video Processing Unit

Tried disconnecting it all. It shouldn't be an issue, it's an Antec 400+W PSU