There is this feature called Eyefinity for ATI cards. Is this what you are talking about? If so, search up Eyefinity in Youtube and you'll surely find gameplay of an Eyefinity game. So far I have seen GRID: Race driver and Dragon Age: Origins.
EDIT: As long as you have Eyefinity enabled, 3 screens will show everything. (Including your desktop and games) Note: Works on Dual or Triple monitors that all have the exact same resolution.