Once you have both monitors connected, right click anywhere on the desktop (under windows 7) and select resolution.
-Select the resolution you would like each monitor to use (works best with identical resolutions)
-Select which monitor will be your main display (this is the one that will have the windows taskbar and start button)
-you can drag and drop the monitors in the window at the top to change where the monitors are situated on the windows desktop
press and hold the windows key, then press "p". select extend from the menu.
enjoy!
p.s.
Dual = two
Duel = a fight