You have a 8800 GT. I have a 8400 GS and the game ran smoothly in some levels except in the jungles at 800 X 600 resolution.
Also I have a E7500 CPU (Intel) @ 2.93 GHz. Mostly I think its your processor. Its quite outdated. Do you have the latest NVIDIA 260.99 WHQL drivers for your 8800 GT ??
Maybe thats the problem. Also, note, Black Ops does not run much good with Dual Core Processors like yours or mine.