If a user has registered through the front end, you can go to the users panel in the admin section and promote them to be an administrator. The settings will not be available to the user then.
Your friends over here at WebAssist! These Dreamweaver extensions will assist you in building unlimited, custom websites.
These out-of-the-box solutions provide you proven, tested applications that can be up and running now. Build a store, a gallery, or a web-based email solution.