Why is my COD4 demo lagging like CRAZY?

[Kromis]

I checked FiringSquad for their specs and apparently, they were able to run it flawlessly. I have the 163.75 driver, same as them, and for some reason it just lags like mad. I have an 8800GTS @ stock speeds and a E4300 @ 3.2 Ghz.

I also play at 1680*1050. No vertical sync. The rest of the settings are the same as FiringSquad's.

Can someone tell me what is wrong? Running this on Vista 32-bit, by the way.