I have a GT220, and had similar problems. I noticed a few things were set default by the control panel that weren't optimal for gaming.
Anisotropic Off
Antialiasing Off
Make sure your display mode is set for single monitor display if you're not running more than one. I've only ever ran one, but for some reason, game was defaulted for multiple monitors.
Texture Filtering on High Performance
and be sure your VSynch is forced on. Most monitors can't display over 60FPS, and your eye can't tell the difference. When I first got this video card, it was hitting 220-250 FPS and getting extremely hot. This did nothing for the game, just wasted resources on the card.
After fiddling around I was able to turn on most everything and run at a 512 Texture. Unfortunately, it still gives 10-15FPS skips in frame rate every few seconds if I run HiRes.