Read about the "enhancements" of various Geforce drivers at www.geforcefaq.com. Search "what drivers"
Also, take a look at a benchmark comparision of various experimental Geforce drivers at www.NVGuru.com. Look for the headline, "Updated Detonator Comparison", and follow the links.
You'll find that from 6.32 to 7.17, 6.50 is the fastest. I believe at NVGuru you will find another article that mentions Microsoft gives the nod to 6.67 for stability. 6.31 is still the latest official version from nVidia.
Hope this helps
Phsstpok
Remember, up the creek without a paddle is better than up the creek without a canoe.