I know I've told this one before, but:

I get a "I can't get the system to turn on.", and when I arrive the guy isn;t there, but his gal driend is, and she is watching TV on the system.

He walks in and says "Ah, you got it working, what did you do?".

I told him to ask her, and she says "I pushed this button that has ON printed on it.".

Didn't bill him since the laugh riot afterwards made my day.