Khatra.exe is a W32 trojan which is the most annoying virus i had ever seen. It appears as khatra.exe, ghost.exe or Xplorer.exe. This virus disable the Task manager and Registry Editor permanently. I was struggling with this idiot for a few days. So I had found this  new method to remove it from the hard drive.

Steps:
1) To Enable Task manager,
Go To Start> Run

 Enter gpedit.msc in the Open box and click OK
 Select User Configuration > Select Administrative Templates> Select System > Select Ctrl+Alt+Delete options> Select Remove Task Manager> Double-click the Remove Task Manager option. Now your Task manager is Enabled.