Hehe, working as a computer technician we really used to play about with machines ot just plain f*ck up.
Pulling IDE cables out of drives whilst the machine is turned on (on most Windows machines the system just hangs till you plug it back in and the machine runs like nothing has happened - who says Windows isn`t stable, lol).
Pulling out video cards whilst machines have been turned on.
Putting magnets to the bosses hard drive (held all the transaction records as the machine was used as a till) after she screwed us all for money.
Dropping a monitor down a flight of stairs and then giving it to out boss to take to a customers house to install (when turned on it started sparking and smoke came form the top).
And probably the biggest f*ck up of all leaving a laptop top on a work bench and then accidently dropping a screwdriver which went through the screen (not my fault, honest )
You name it it had been done.
A funny customer story going back to last Christmas, a customer bought a £3500 Pc for his son to act us a home recording studio, a week later the machine came back in crawling (it took over 20 mins to boot into windows), fault, the hard drive had been filled with MP3`s and porn.
Seeing as the parents were so abusive saying we sold them defective products we took great delight in demonstarting what was wrong
