Hi,
Right click on your desktop and click properties, then click settings tab at the top, click advanced button at the bottom, click on the Nvidia or GeForce tab at top, if you have one of the latest detonator drivers installed it should open a quick access panel on the left of that window, click "nView Display Mode", under nView modes in the middle of the window you should select "Single Display"
Let us know if it doesn't work
CIAO