Adding a THIRD monitor -- do I need any additional hardware?

[teddyFBI]

So I'm happily dual-monitoring with my 2001fps with the dual-DVI Matrox video card I bought...now I want to add a 3rd one. Am I going to need to purchase some newfangled 3-output video card...? Or can I just plug my 3rd monitor into the existing VGA port on the onboard graphics card that came preinstalled on the computer??

And if I CAN, what, if anything, do I need to do after I plug that 3rd sucker in? What settings do I then need to adjust to get all 3 of the monitors working in harmony?
(I ask because I thought I remembered that the first thing I had to do to get my Matrox graphics card working was DISABLE the onboard video...if that's the case, then won't I have to RE-enable it??)