On being stupid with my own hardware
I built a mame machine into a dead arcade cabinet for the breakroom of a former employer. Well, it was for me, and for a few others that had regularly been playing an original upright Vs Super Mario Brothers, and then later an original Marble Madness (gimme that double WAND).
I was in the middle of a system upgrade (old motherboard died...) and I had a pretty good chance that my very-small-linux-install on the drive would 'just work'
I had the whole thing apart and was about to connect power to the IDE drive the system ran on... and while distractedly talking to a co-worker, I attached the new drive, while the other system was still on. It fried the drive...
What would probably have been a 5 minute hardware swap turned into a several-hour reinstall/re-setup of my mame front end (AdvanceMENU), on a new drive, which I fortunately had laying around.
What did I learn? Turn off the power. Sigh. this is why I dont want to fix your computer.