Here are two pages showing how to control access to the Internet Explorer setup and control panel functions (Tools > Internet Options). You may be able to use this information to reverse changes that may have been made. They require use of the Registry so if you decide to explore this option make sure to set a Restore Point before you start.
http://www.winguides.com/registry/display.php/537/
http://www.winguides.com/registry/display.php/797/