Have you updated your graphics driver lately ?
I found out by accident that there is a brand new driver for my GeForce 8800 GT out.
Nvidia Driver GeForce 8800 GT
GeForce Release 181 WHQL
Version: 181.20
Release Date: January 8, 2009
Operating System: Windows Vista 32-bit
Language: U.S. English
File Size: 77.6 MB
First thing I've tested, after updating, was Crysis because that worked just about on my PC.
Someone smack my face please but I think there's a big difference now ... smoother, even despite all settings set to high (but AA off of course).
Cool.