I can't enter this, since it was my mother who repaired the problem, but this should give someone a smile.
I was 11 or 12 (I can't remember the exact age) at the time of the incident. At that present stage I thought I knew EVERYTHING about computers (Pfft) and I had my own computer (although I hadn't built it) running for a long time with no problem. Then one day I had a problem with my monitor, it wasn't turning on. So me beginning the 'computer know-it-all', I decided to fix it without anyone's help. I did my usual thing of checking the monitor cables for power etc, that didn't help. I tried the usual thing of whacking the monitor (yes, I used to think that would help with fixing a computer). And then after about 10 minutes of checking things and whacking my computer and monitor, I noticed a little red switch at the back of my computer saying 230v. I thought I haven't tried that so I flicked it so it now said 120v. I think you can imagine the blue light that came out of the back of the computer... and now the computer wouldn't turn on as well, plus there was a smokey smell coming from the back. After a couple of hours... I finally told my father who got very angry to say the least. After my mother investigated the powerboard from the powersupply, she saw the fuse had blown and said she could fix it. 3 months later (to teach me a lesson I suspect), she solders in a quick fuse changer and puts in a new fuse, and also finds out that the problem with the monitor was the cable was fault... and also the VGA cable. We replaced the entire monitor only a month later when the VGA cable broke apart.
Moral of the story, the switch on the PSU can make a computer go BOOM!