Have you tried nVidia's latest drivers? They are v77.77 click here. The version on the Leadtek site for Win2K/XP is 66.93 click here.
If you still have problems, with the new drivers installed run a DirectX diagnostic test:
Start->Run. Type dxdiag in the box & OK.
Click the Display tab & check whether DirectX Features are all Enabled (try enabling them if disabled).
Click the buttons on the right to test DirectDraw & Direct3D.
If you have any problems, let us know the error
code number(s). Good luck, G