You need to install the video card drivers. If the computer is a Dell, those drivers will be on a disk, probably labeled "Resource," that came with the computer.
Otherwise, if there is no disk that came with the computer with video drivers or graphic drivers or something similar on the label, you'll need to know the make and model of the video card (called Display Adapter in Device Manager) in order to download the correct drivers from the card's manufacturer's website.
If you don't know that information, download, install and run
Belarc Advisor (it's free). It will inventory your computer and hopefully tell you the make and model of the video card.