I have win2k and a GeForce2 GTS also.. and I had a similar problem. First, get the latest NVIDIA drivers. Then, right click on your desktop, go to properties->settings->advanced, then go to the troubleshooting tab, and turn your hardware acceleration slider down a notch. If that doesn't help, try another notch.
I've noticed with this video card, and win2k a few games require I turn hardware acceleration at least half off for them to display properly, and down one notch to stop the little flickers.
Hope that helps.