Please help, I'm at the end of my tether with my new PC. It is my first PC build. The system runs like a dream until I come to play games. If I run any game at AGP8x, the game will crash. Screen freezes then monitor will go into permanent sleep mode, or I get a VPU recover error. My board and graphics card both support AGP8x. If I turn the AGP down to 4x then games will run, although I have still had problems with 4x on high end games such as Far Cry.

Have seen many other people on the web with similar problems but as yet I am unable to find a solution. So far I have tried the following:

Updating all drivers - display, chipset, sound, etc.
Updating BIOS
Purchasing new PSU
Increasing AGP aperture size
Trying one memory stick at a time
Increasing AGP voltage settings
Trying my friends graphics card

Tweaking some of these things seem to have improved the problem but not solved it. For example before I started tweaking, I was unable to play FIFA Football 2006 on AGPx4 but now I can. However, soon as I play it on AGPx8, it crashes straight away.

System is as follows:

Giga-Byte K8NS-Ultra 939
AMD Athlon 64 3200 32/64Bit CPU S939
1GB 184-pin DIMM DDR PC3200 CL=3 UNBUFFERED NON-ECC DDR400
160Gb Maxtor Diamondmax Plus 10 (7200rpm,8MB) "Sabre" SATA NCQ
ATI Radeon 9600 256MB 128Bit DDR DRAM
Sony DWQ28ASV 16x16x4 DVD±RW Dble Dual Layer DVD Writer OEM UK
Jeantech PSU 450W

I have 2 case fans. All temps appear OK. I have also tried (as mentioned above) my friends gfx card in my machine, that was a GeForce 4200Ti, I experienced similar peoblems with this card.

Any help will be greatly appreciated.