Recently I installed a new power supply and an Evga 8800GTS 320mb on my friends PC.  Everything is working properly but he is only getting 80 fps on Counter Strike Source, where I get 100+ with my 6800 card. He has tried it on medium settings but it is still the same result. It is not a stable FPS either, It drops to around 40 at times. Vsync is off so the fps is not capped. And we have the latest drivers.

He is running Vista Ultimate with aero turned off.
2.8GHz Pentium D.
Nvidia 8800 GTS 320mb
2 gigs of ram

Also note that his computer is a HP.

The stock core clocks are way below what they should be aswell, And when we try to overclock it he gets a driver error on Windows Vista.

Help would be appreciated although I cant do anything until I go over there tomorrow.