Task Manager has been disabled by your administrator

I’m guessing a piece of spyware did this to disallow terminating of their task.

Here’s how to re-enable the ctrl-alt-delete sequence:

Go to this key using regedit:

HKCU \ Software \ Microsoft \ Windows \ CurrentVersion \ Policies\ System

Set the DisableTaskMgr key to 0 and that will re-enable it.

More methods here: