Copy the service tag information from the bottom of your laptop and point your browser to http://support.dell.com
and enter the service tag where prompted. When your laptop shows up on the screen, select drivers and downloads and then select the OS you are using (Windows 7), then find the drivers for your graphics chip under video.
The only problem w/Darkness' solution is you must know the video chipset for your lappy. Entering your service tag info circumvents this problem.