I am guessing that it has the VGA, DVI, and S-video output on the back of the video card?
You need to hook up one monitor to the DVI and one to the AGP. The nVidia drivers come with the needed software, nView.
If you are running CRT's then you will need a DVI to VGA adapter, ATI cards come with them =) I had a Geforce 4ti card, I had to buy an adapter, cost me like 20 bucks.
If you are running LCDs it should have a VGA or DVI output on the monitor itself, connect one monitor to the VGA and the other to the DVI.
Once connected boot up, isntall drivers if not installed already. Right click on your desktop>properties>settings, if you see two monitors that displays the resolution changes, then click on the one that is grayed it, there should be a check box saying 'stretch my desktop to this monitor' check it. There is also the nView configuration which can be accessed from Control Panel. Depending on what OS and card you have (specifically) things might be different.
Hope I helped..