Can anyone tell me how to restrict users from changing desktop settings in Windows 7 Home version?

I try to manage a Windows 7 computer that has a common user login because several people need to be able to use the same files. It’s the Home version, not the Professional version. We have one user who can’t resist tinkering, and he’s screwed it up again. (He’s also the reason I have to have a common user – he’d save the files to his personal folders and no one else could get to them. Grrr.) I’d like to restrict his ability to make ANY changes to the desktop settings, but the only instructions I’m finding use a group policy manager that’s not available in the Home version. Any ideas?