SB75G2 - X800XT Problem

Ive just recently upgraded my 9800XT to a X800XT but ive had a few problems since upgrading. Since reinstalling I have installed CS (not CS:S) and BF2 Demo and Ive found that I keep freezing after a random amount of time in CS. I have the latest gfx drivers, latest chipset driver, latest sound drivers, and my gfx card isnt overheating because it runs idle at 30 odd and a max of 50 odd. Yet it still keeps freezing in a game that isnt that graphically chellenging.

Heres the funny thing, I play the BF2 demo on max settings with 4x AA and it doesnt crash....well it hasnt yet anyway, and Ive played them both about the same amount. Yet it does on a game that was made in 1999! As soon as I go into CS i can see some dodgy texture flashing and after a random time I freeze and my scrren flicks off and on, off and on until I just have to restart. One time it did it and VPU recovered and I managed to play on, then 5 mins later it crashed and I had to restart.

Some people have told me it could be that the Gfx card isnt getting enough power, but I read in a review that the X800XT PE draws marginally less power than the 9800XT which was my previous card! And even if it was this, why would BF2 run fine and CS crash, ud expect BF2 to crash well quick with the settings i have it set on.

Other things ive tried is downgrading to Omega and Cat 5.5, none worked, same probs. I also disbaled Fast Writes, also no difference.

If anyone could help me on this it would be helpful. Here is my spec:

Shuttle SB75G2
P4 3.2 Ghz
2GB DDR400 Ram
X800XT PE (Not OC!)

One more thing, one of my friends has the same spec as me except with less memory and a 3ghz proc not 3.2 and his CS runs fine

Any assistance would be good, thanks!