Not a mobo, not even a computer, but.....
When I was 17 I drove round to a friend's house, as he'd agreed to help me fit my car stereo head unit and CD changer (almost 400 quid's worth). I asked him because he had taught himself A-level electronics (succesfully I might add, he got an A) and he had a multimeter, and the wiring loom in the car was a complete maze. Within seconds of having the thing installed smoke poured out of the dash ('console' in US?).
One thing I learned that day (and have since confirmed) people who are good at theory (such as in my Physics dept) are not always so good at the practical side of things!
I also had a capacitor blow up in my eye at an electronics club at mjy school, because some tit had it connected to a dynamo that he was cranking like crazy...
I was lucky!
