I need help with Inno3D Fx 5600

hello.... can anyone help me out with my video card problem? Im using my video card under window xp pro but each time i play with 3d games (ie. command and conquer, warcraft) the screen turns distorted after a few minutes. In warcraft the mesh of the 3d characrters suddenly gets out of propoertions and in c&c the resolution and graphics drops.

I've been wondering if this has something to do with nvidia driver for xp because in windows me i didnt experience any of those things. 2d graphics works fine. Can anyone help me out to make this run in xp.