We can start by doing some simple maintenance on it. Try downloading updates to your antispyware and virus program and run them again. If that didn't detect anything, the try doing the basic stuff like:
Delete all temp files in Windows, delete temporary internet files, delete all off-line content, cookies, etc. Run a disk cleanup and degfrag your hard drive.
I've got new drivers for my 6600GT and working great. But then again, it depends on your system.