Task Manager has been disabled by your administrator" error message

Solution No.1:-

  a. Go to "Start" -> "Run" -> Write "Gpedit.msc" and press on "Enter" button.

         b. Navigate to "User Configuration" -> "Administrative Templates" -> "System" -> "Ctrl+Alt+Del Options"

         c. In the right side of the screen verity that "Remove Task Manager"" option set to "Disable" or "Not Configured".

         d. Close "Gpedit.msc" MMC.

         e. Go to "Start" -> "Run" -> Write "gpupdate /force" and press on "Enter" button.

         Note: If you are using Windows 2000, please follow KB q227302 instead stage "e".

                Using SECEDIT to Force a Group Policy Refresh Immediately
                http://support.microsoft.com/kb/q227302/
Solution No 2:-

Click Start, Run and type this command exactly as given below: (better - Copy and paste)

Method 2

Download and run this REG fix and double-click it.

Method 3

• Click Start, Run and type Regedit.exe
• Navigate to the following branch:

HKEY_CURRENT_USER \ Software \ Microsoft \ Windows \ CurrentVersion \ Policies\ System

• In the right-pane, delete the value named DisableTaskMgr
• Close Regedit.exe

Solution No 3:-
    Start>>Run>>gpedit.msc>>System>>Prevent Access to Registry Editing Tools (set this to DISABLED)