I want to add a second display to a Mac Mini (circa 2007)
 

The mac mini is a 2 GHz Intel Core duo. I have one 20 inch cinema display plugged into the dvi port on the mini and I would like to add a second 20' cinema display using a displaylink usb to dvi multi-display adapter.

I purchased the Plugable USB 2.0 Graphics Adapter, and downloaded the displaylink driver, but the mini fails to recognize the additional monitor. Do I need a different product? Any help would be fantastic.