When I update my nVidia drivers, I do the following:
Set my video properties to VGA 800x600.
Run the nVidia uninstall program to remove the current drivers/tools.
Reboot the machine.
Run Driver Cleaner Pro to remove the remaining bits & pieces.
Available here:
http://downloads.guru3d.com/download.php?det=745
Reboot again.
Install the new drivers.
Reboot as required.
At the moment I don't remember vhich nVidia drivers I'm running; I'm at the office.
Hope this helps.