Or simply make an executable file that launches with the blue screen of death that self stretches itself to the users screen settings. When the application is executed it then disabled task manager. Just make a second file that re-enables the task manager registry as a "Cure".
Be fun because you can setup the executable to look like one of their most used programs or browsers and replace with that.
I would be a dick and do this to leave less suspicion,
Change their Google Chrome with the executable, add a delay to the new "Fake blue screen" say 10 minutes.
Do this, System.Diagnostics.Process.Start("www.google.com");
Then have the executable run in the background so when the time is reached it then disables task manager and then shows the blue screen.
Or hook the keyboard so when something like a porn site is entered it gives the blue screen of death.
**midnight trolling**