Hello,
Windows Update does NOT carry the latest set of drivers. They are at least a month to 2 months behind. A new driver will be released and have fixes for known issues and it will take up to 2 months maybe more before they are on Windows Update. Not to mention the only drivers on there are the ones that are completely certified by Microsoft. While not every driver released is.
You will be waiting a long time for the driver to hit Windows Update. In that time 2 or even 3 new sets will have been out. Use the nVidia site. It is faster and much better than expecting windows Update to do everything for you.
Cheers,
Mak