7800 Series Issues with ABit KN8 Ultra

[shaithis]

This is driving me nuts, any help would be most appreciated!!

I recently decided to upgrade my mothers PC with some bits and pieces I have had lying around. Some of those items were:

ABit KN8 Ultra mobo with latest BIOS (19)
X2 3800 CPU
GeForce 7800GT

All seemed OK when setting the BIOS up but then when booting Windows XP the screen corrupts and it never enters windows.

I thought the card had gone so purchased a 7800GTX from these forums, it does exactly the same.

Tried a 7600GS from another machine and it booted strait into Windows without a hitch....

Any idea? I am completely stumped.

[BUFF]

power supply?

[GSte]

My second rig has a KN8 Sli and 7800GT and works fine, as Buff says, PSU?

[shaithis]

Forgot to mention, I thought it was PSU initially and threw a brand new 700W PSU in (a Jeantech 700W Storm from PC World but still the same PSU I have seen others buy and run 8800GTXs from)