Had a question about it. Does the same image show up on both monitors, or is it possible to like be playing a game on one monitor, and surfing the web on another?
It's part of the driver suite for an Nvidia card. It's called Nview. you can have it duplicate/Clone the desktop or be an extension of the desktop. you can even have different resolutions and refresh rate for each monitor.
I'm Sure ATI has the same thing. Just look through the display's control panel. I'm sure you will spot it.