Here are my Nvidia settings for my GeForce 6800GT agp card using the 66.93 drivers for my Geforce 6800gt card, not sure of what drivers you should be using with your card. I'm hoping the card isn't overheating.

Antialiasing settings;   8xS
Anisotropic Filtering;   16x
Image settings;          Quality
Vertical Sync;            On  (LCD monitor)
Force mipmaps;         none
Conformant texture Clamp;  On
Extension limit;          Off
Hardware acceleration; Single Display mode
Trilinear optimization;  On
Anisotropic mip filter optimization; On
Anisotropic sample optimization; On

I hope this helps. UT99 I run it under OpenGL.