go to a command line and type
gpedit.msc
and hit enter
A window should open and look in the list for User Configuration and than below it look for Administrator Templates and than System.
Once that is open look on the list on the right side of the screen and find the line that says....
Prevent access to the registry editing tools double click it and than set it to disable. After close all the windows.
The registry editing should now work.