Enable Task Manager if being Disabled

Click Start then Run.
Enter gpedit.msc at the command line and click OK. This will open the Group Policy settings window
Select User Configuration | Administrative Templates | System | Ctrl+Alt+Delete Options | Remove Task Manager.
Double-click the Remove Task Manager option from the Group Policy menu. You can then disable, enable, or set the policy to Not Configured. Remember: Since the policy in question is called Remove Task Manager, by disabling the policy, you are actually enabling the Task Manager.