I know you can disable IE (and any other application) with group policies by specifying the executable to not run, but I'm not sure where it's located. If you choose to go this route, look for a policy that states something like "Do not allow Windows applications to run." Also, I don't know if disabling IE will have any other adverse affects since it's so integrated into the OS. Test it first.
A simpler option might be to logon to that machine as administrator and change the permissions of iexplore.exe to allow only the administrator access (this assumes the operator is not an adminstrator). Locate iexplore.exe (c:\program files\internet explorer) Right click, properties, security tab, and remove all except adminstrators. They will be denied access when trying to launch Internet Explorer. Hope this helps.