Task manager has been disabled by your Administrator

This error happens due to some malware or spyware software putting some registry restrictions(DisableTaskMgr restriction) so that one can’t trace or remove them from the system startup.You can follow any of the resolution methods given below:

Method 1: Using the Group Policy Editor

• Click on Windows Vista/XP Start, Run, type gpedit.msc and click OK.
• Navigate to this branch:
• User Configuration > Administrative Templates > System > Ctrl+Alt+Delete Options > Remove Task Manager
• Double-click the Remove Task Manager option.
• Set the policy to Not Configured.
  

Method 2: Using the Windows Registry Editor

• Click on Start, Run, and type regedit.exe and press Enter
• Navigate to the following branch
• HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\System
• In the right pane, find and delete the value named DisableTaskMgr
• Close the Windows registry editor
• Reboot you computer for the changes

Method 3: Using the Command Prompt

• Click “Start > Run” and type following command exactly as given below in one sentences and click OK.
  
  • REG add HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\System /v DisableTaskMgr /t REG_DWORD /d 0 /f