That's a very common problem for Windows users. Many times when you try to open Task Manager, you find that "Task Manager" option has been grayed out:

Also when you try to run it by typing "taskmgr" in RUN dialog box, Windows shows following error message:

Task Manager has been disabled by your administrator.

1. Type regedit in RUN dialog box or Startmenu Search box and press Enter. It'll open Registry Editor. If Registry editor is also disabled, then follow instructions given in following tutorial:

How to Enable Tools -> Folder Options and Registry Editor in Windows

2. Now go to following keys one by one:

HKEY_CURRENT_USER\Software\Microsoft\Windows\Curre ntVersion\Policies\System
HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\Curr entVersion\Policies\System
HKEY_USERS\.default\Software\Microsoft\Windows\Cur rentVersion\Policies\System

and look for a DWORD value "DisableTaskMgr" in right-side pane. If you find it, delete it.

3. That's it. Now Task Manager will be enabled.

YOU ARE DONE