Yes, the guy that knows just enough to be dangerous

>The absolute worst user is the user who is, in his own head, the local computer guru. The Kind of guy who knows close to nothing about computers, but who has been lucky a few times. The kind of guy who wastes hours destroying the computers or the setups, before he insists that the error was caused by a bad computer, and should be fixed on the guarantee. I had one such user, luckily I managed to persuade him into finding another supplier.