This could be a quirk of the Windows performance test. Try to run Windows Update (if you have not yet), and see if this fixes things when you re-run the tests. If you are actually using the nVidia drivers, you don't really have an issue.
I have seen people with issues running the 3D testing when it errors out, although there is nothing wrong with the system aside from that.
If it never goes past 1, don't worry about it. If your other programs run great, and Aero actually works, no biggie if the benchmark can't complete properly.