It occurs due to the infected virus on the computer or the system administrator disable it through Regedit or Gpedit.msc.This promblem often occurs in PC and Laptops,mostly it is infected with viruses like Trojan,Worm etc.To solve this you need to follow the steps:
Go to Run button then type Regedit
Look at :
Hkey_Current_Users/Software/Microsoft/Windows/Current Version/Policies/System
Hkey_Local _Machine/Software/Microsoft/Windows/Current Version/Policies/System
Hkey_Users/Software/Microsoft/Windows/Current Version/Policies/System
Find the word "DisableTaskMgr" value and delete it.
Next time Task Manager will open.Thanking You
Go to Run button then type Regedit
Look at :
Hkey_Current_Users/Software/Microsoft/Windows/Current Version/Policies/System
Hkey_Local _Machine/Software/Microsoft/Windows/Current Version/Policies/System
Hkey_Users/Software/Microsoft/Windows/Current Version/Policies/System
Find the word "DisableTaskMgr" value and delete it.
Next time Task Manager will open.Thanking You





