I looked at the video card on the back of our newer computer, and it already has two ports on it! One port is the traditional VGA port, and the other is a newer DVI (Digital Video Interface) port. DVI ports are for flat panel monitors. All I should need to do is buy a $15 adaptor and I should be able to have two monitors running.

This is a picture of both sides of the adaptor. The top port is a VGA port, and the bottom is a DVI port.