The greatest practical joke I never played

This always cheers me up:

At work my team leader wasn't the most technologically comfortable guy (but great with the statistics). Our computers have a screen saver with password that we are supposed to activate whenever we step away, but he didn't always do that... so I had a bit of fun to teach him.

One time I flipped his screen image (only possible with some graphics cards). Another time I changed his background image. I changed some of his Word settings (never noticed because he didn't use it that much). And so on. Never got around to sending a message from his email to everyone offering to buy morning tea through... (although that does happen with someone else I know, which the person has to then provide morning tea as punishment for not locking their computer).

Eventually, he moved on to another job, and on about the last day or so, got to playing with his calculator, and found out that it wasn't working. I tried it, and found that the 0 and 1 button worked, as did some function keys. Odd...

Tick...tick...tick... click!

Changing from binary mode to normal, I fixed his calculator for him. He said it had been like that for two years and he hadn't known how to fix it! (He also looked very suitably shamed.)

I just wished I had been the one to do that...

[END]