There's this thread where G-452 had issues with a 8600 GT.And darkstorme suggested OmegaDrivers.net | ATI/NVIDIA Omega Driver's Home, PC Gaming Drivers & News! for alternatives to the regular nVidea drivers.
For those with an 8800 series card and slow framerates, especially around water scenes or scenes with environemental animation, I recommend using Nhancer, a third-party Nvidia profile editing utility.It gives you finer control over the Nvidia profile options for your games. I found that using Nhancer to force NWN to only use a single core for OpenGL improved my framerate to playable levels.If you are finding that the default Nvidia control panel profile editor doesn't seem to have an affect on your framerate when forcing NWN to run on a single core try Nhancer to do the same thing. Nhancer, for me anyway, has been more reliable at changing the options I want to change when compared with the Nvidia control panel.nHancer - Advanced Control Panel for nVidia Cards
I just reinstalled NWN Diamond on my Windows 7 computer, also with a Nvidia 8800 GTS.I was experiencing the same slow framerate than most in this thread (5 to 20 fps). My driver for the video card are 196.21.I found that when I choose Miles Fast 2d positional audio I am now able to run the game at 30 to 40 fps.From what I understand of the problem, Nvidia made some change to their driver that make some old game like NWN render some of the 3d graphic on the CPU instead of the GPU. That explain why people with really powerfull CPU still get good framerate. This also explain why using Miles audio instead of other 3d audio enable to get faster framerate. 3d audio run on the CPU which leave less CPU cycle to render the graphic.This frustration to have only 30 to 40 fps on a system which should be able to render at 100 fps, but at least it is playable.