I've collected a few tales in the past from numerous helpdesks I have worked with:

A woman phoned saying that she couldn't get her computer to work. further discussions revealed that she was trying to use a "foot pedal". Intrigued by this, the techie went out to investigate and came back in fits of laughter. It turned out that she was so used to using a sewing machine that she had mistaken the mouse for a "foot pedal"!

Another story (probably urban legend) was passed on about a small company who assigned the task of backing up the "important" machine using floppy disks and storing them in a safe place to the young secretary. She was shown the procedure and asked to make copies every weekend. After a few months, the hard-disk failed and and a techie was brought in to replace the disk. No problem, thought the owner as we have plenty of backups to restore from. He called the secretary over and asked her to fetch the latest backup from the safe store. She came back with a big bundle of papers, each with an image of a floppy disk on them. After some explaining, it turned out that she had been photocopying the original backup disks every weekend to make "copies"!

Finally, we have a tail from a computer support line. A frustrated user phoned up to say that his screen had gone blank and he couldn't get the computer to work. After some discussion the support engineer asked the user if the "power light" was on. "No" came the reply. The engineer then asked if the obvious- was the computer plugged in and switched on. "I think so" came the reply. The engineer then asked the user to check to see if it was, as a power lead not connected would stop the computer from working. "I can't see" came the reply. "Why not?" asked the engineer. "It's too dark - all the lights have gone out." the user replied. Thinking this rather odd, the engineer asked the user to switch a light on so he could check the cables. "I can't do that" said the user, "we've had a power cut..."