I dont remember off hand if the 8800 is capeable of DX10
goto start|run and type dxdiag and see what version that you have and do the tests to see if you can run all of them.
then post back.
There was a time when changing nvidia drivers messed up direct x a little and the reinstall will fix it.
Strangely enough bad sound drivers can cause direct x to mess with video but i havent seen that much lately.