If for some reason you’d like to restrict users from changing Sound Scheme in Windows 7, here is how you can do it via Registry Editor or Group Policy Editor.
Open regedit and navigate to the following key:
Right click Windows in the left pane and create a new key and name it as Personalization.
Now select Personalization & in the right pane create a new DWord NoChangingSoundScheme & give it a value ‘1‘.
To enable it back, simply give it a value ’0′ or delete the NoChangingSoundScheme DWord!
Alternatively type gpedit.msc in start search and hit Enter to open the Group Policy Editor.
Navigate to User Configuration > Administrative Templates > Control Panel > Personalization.
Now double click Prevent changing sounds in the right pane.
This will open a new window. Here, select Enabled. Click Apply/OK > Exit.
This setting prevents users from changing the sound scheme.
By default, users can use the Sounds tab in the Sound Control Panel to add, remove, or change the system Sound Scheme.
If you enable this setting, none of the Sound Scheme settings can be changed by the user.
As you can see, you can set several restrictions pertaining to Personalization here.