PC help: Re-enable Task Manager

Q If I press the Control, Alt and Delete keys together to display the Task Manager a window appears saying that Task Manager has been disabled by the Administrator.
As I am the sole user of this PC I do not know how it could have been disabled. Right-clicking on the Taskbar shows the Task Manager greyed out.
How can I reactivate it, please?
Arthur Newby

A Deactivating the Task Manager is a useful way of making a computer more secure. This option is set in the Registry, and we have heard from several people who have had problems with it changing. Thankfully it is simple to put right. This fix does involve changing the Registry so make sure all your files are backed up and create a Restore Point before going any further. Problems are unlikely but it pays to be prepared.

Left-click on the Start button and then on Run. Type regedit and press Enter. Click on the small plus icons next to HKEY_CURRENT_USER and then Software, Microsoft, Windows, CurrentVersion and Policies. Left-click on System. Don’t worry if you can’t see it; just skip to the next paragraph. Double-click on the icon in the right-hand side of the window called DisableTaskMgr. Type 0 in the Value data box and then click on OK. Click on the File menu and select Exit.

The location in the Registry described above only works for the current user and the change may have been made for all users. If so, repeat the instructions above but starting from the HKEY_LOCAL_ MACHINE icon in the Registry Editor.