Gameplay is very jerky after installing 7600GT

[NoodleTech]

Hi, my friend purchased my evga 7600GT. He was upgrading from a 6600GT. The 7600GT gave me no problems while I was using it. I got a consistent 100fps in counter-strike even while running through high quality smokes. Now after my friend installed it in his computer, he says his fps fluctuates in counter-strike. He says it goes from 100 to 20 to 10 to 60 and all over the place. He says when he runs its very jerky and there is a delay after shooting and everything isn't smooth. He has this problem with almost every steam game he plays. Even non-graphic intensive games such as step-mania give him this problem. He says he never had these problems with his 6600GT.

I had him try uninstalling and reinstalling the forceware drivers, but this didn't help. Anybody know what might be causing these problems? Thanks!

 

[Onus]

What are the rest of his system specs? What mobo does he have, what CPU, and how much RAM?

 

[NoodleTech]

Pentium D 820 2.80GHz
ECS 945P-A
OCZ DDR2-4300 1GB