The reg file in the ZIP download below will restore this default Explorer key and entries back to your registry. After you have extracted the reg file from the ZIP, just double click on it to merge and approve.
Hope this helps,
Try doing the manual METHOD TWO at this registry location as well. It should hide it for all users.
In the left pane, you would right click on Policies, and click on New and Key. Type Explorer, and press Enter.