...be brave.....and daring; you have to create the 'Value'
User Key: [HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\
Explorer]
Value Name: NoViewContextMenu
Data Type: REG_DWORD (DWORD Value)
Value Data: (0 = disabled, 1 = enabled)
You need to create the last three entries by using right clicks in Regedit...forget about the 'Local Machine' and see if this works after a re-boot. Make life easy and save (export) the entire entry as a reg file and if something goes wrong just double click it and all is returned to previous entries. I'm not sure if you name it that , that the value shouldn't be '1' so try both before restoring.