in windows 7 and vista
Windows Sideshow is a new technology that enables users to see what is on their PC or laptops, even if they are turned off (asleep,on hibernation, or any other state), with the help of a simple mobile phone or any other device that supports windows sideshow ( laptop lids, PDA, any kind of gadgets possible with a display ).
So, if you have a device that is compatible with Windows Sideshow and your PC has running Windows 7 or Vista, follow the lines bellow in order to activate or deactivate Windows Sideshow:
◦Open the Local Group Policy Editor. (Read here how to do that)
◦Expand to the following tree branch: User Configuration\Administrative Templates\Windows Components\Windows Sideshow
◦Double click on the Turn off Windows Sideshow option in the right pane.
◦To DISABLE or turn OFF Sideshow select the enable radio button
◦To ENABLE or turn ON Sideshow select the disabled or .not configured radio button
◦Click OK
(http://i50.tinypic.com/xo3bia.jpg)