Connecting a computer to two monitors

I was given a Dell Dimension 4550 computer with two monitors. Unfortunately, I seem to be missing a component to connect them properly. The computer has a different DVI connector than the two monitors. (The connectors on the monitors appear that they would connect to a different Dell Dimension 8200 computer that I own.)
Is there something I can buy that would act as an interface? It would connect to the computer and then connect to both monitors?
PS Since this computer was alredy operating with these two monitors, I will assume that it has the necessary internal cards, etc. to allow the use of two monitors.