Affter deploying a terminal server alot of people leave this as an oversight. If you do not disable the registry editor or restrict it then ANY user can come along, run it and tamper with the servers registry. Here is a quick way to stop useres running regedit on a remotes desktop server / terminal server.
1) Browse to %SystemRoot%\Windows\system32
2) Right click on regedt32.exe and then select properties
3) Then select the security tab
4) Remove anyone who should not be in there and make sure that only admins are in there
6) Click apply and then select ok
7) Do this also for Regedit.exe ,it will be in the same location