This policy setting allows you to turn off desktop gadgets that have been installed by the user.If you enable this setting Windows will not run any user-installed gadgets.If you disable or do not configure this setting Windows will run user-installed gadgets.The default is for Windows to run user installed gadgets.
Policy path:
Windows Components\Desktop Gadgets 
Scope:
Machine 
Supported on:
Windows Server 2008 Windows 7 and Windows Vista 
Registry settings:
HKLM\Software\Microsoft\Windows\CurrentVersion\Policies\Windows\Sidebar!TurnOffUserInstalledGadgets 
Filename:
Sidebar.admx 
