How To Enable Or Disable Changing Desktop Background In Windows 7?
You may want to prevent users of your PC from changing the desktop background. Windows 7 lets you do that. Follow these simple steps to disable changing desktop background in Windows 7.
1. Login to Windows with Administrator rights.
2. Key-in gpedit.msc in the Start menu search box and hit enter.
3. In the left pane of the Local Group Policy Editor window, propagate to:
User Configuration > Administrative Templates > Control Panel > Personalization
4. Look for “Prevent changing desktop background” in the right pane and double-click on it.

5. In the “Prevent changing desktop background” window, turn on “Enabled” and click OK.

That’s it. The option “Desktop Background Slide Show” will now grayed out. Also right-click on any image and “Set as desktop background” will do nothing.
In future if you want to enable changing the desktop background image again, follow the same steps. In step 5, choose option “Not Configured” and Click OK.