To enable dual display mode in windows...

1. Right Click on the desktop and select Properties.
2. In Display Properties, Choose the Settings Tab.
3. You will see a graphical representation of a monitor with two boxes inside. (1 is primary, 2 is secondary)
4. Click on the second display.
4. Select Extend my Windows desktop to this monitor, and then click OK.
5. To adjust the color depth on the new monitor, use the Color Quality drop-down list box. To adjust the resolution, use the Screen Resolution slider.
6. Verify that the on-screen arrangement of the monitors matches the physical configuration of your monitors. This can be changed by dragging the icon of the monitor to the location on the screen that corresponds to the location of the monitor on your desk.