Applying policies via the registry

[Nuclear Krusader]

Is there any way to prevent a registry key from being changed?

I'm trying to prevent the custom logon background from being set back to Windows' default every time the user changes the theme. In Windows 7 Business and Ultimate one has the policy editor which has an option to prevent the custom background from being reset, but Windows 7 Home POSmium doesn't have the policy editor.

I either need to find/create a registry key that gives me the ability to do what M$ suggests here, or find a way to lock the OEMBackground value so that it's never changed back to 0.

Any useful input is greatly appreciated.