I take it that the laptop is using the generic VGA drivers
for your graphics controller.
Dell does not list any Windows 7 drivers, but you could try the Vista ones: Drivers & Downloads
If they install, you may be able to update then via WIndows Update or with the latest drivers from www.nvidia.com
If the Vista drivers won't install, things get more complex. It's common for laptop makers to use custom device IDs for their graphics controllers, so standard installers may not recognize the controller.