Open the Start Menu and enter 'gpedit.msc' into the Search (Run) box and hit Enter.
This opens the Local Group Policy Editor, navigate to :
UserConfiguration \ Administrative Templates \ Control Panel \ Personalization.
Then in the right column double-click on:
Prevent Changing Theme and change the settings as required...
You can also change the following settings:
Prevent Changing Desktop Background
Prevent Changing Screensaver
Prevent Changing Sounds
Prevent Changing Color Scheme
Prevent Changing Visual Style for Windows and ButtonsEnable Screensaver
Prohibit Selection of Visual Style Font Size
Prevent Changing Window Color and Appearance
Prevent Changing Desktop icons
Prevent Changing Mouse Pointers
Password Protect Screensaver
Screensaver Timeout
Force Specific Screensaver
Load Specific Theme
Force a Specific Visual Style File or Force Windows Classic
