Hello and Welcome to TSF,
Go here and download the driver:
http://www.nvidia.com/object/winvista_x86_185.85_whql.html
1. uninstall video driver from add/remove
2. check in device manager under "display" that it is gone. If not, uninstall it there too.
3. reboot pc, if an new found hardware wizard box opens, cancel it out.
4. Install driver ( file you downloaded )
5. reboot pc
6. Configure the displays ( display 1, Display 2) one for desktop and the other for
game playing or surfing, whichever.
7. To configure, open up display settings or Nvidia control panel whichever one you have it set on or using.