This one isn't an urban legend, but a stupid friend.
I was helping one of my friends build a new computer one time. We went and picked out all the stuff, and the next day I was going to come over to help him build it. Well, he decided to take matters into his own hands and put the thing together. I decided to have a bit of faith in him and try to install the OS without checking his handy work (I mean, dude is a cop. I figure if they let him have a gun, I could trust him on this). I try to get the thing booted, yet the floppy drive won't work. I'm like, what the hell????
I open the machine, and he has the floppy hooked up to one of those floppy cables with two connectors. The floppy is on the end and hooked up right, but on the second connector he has connected an IDE Zip Drive. Yes folks, IDE. Obviously the IDE connector on the back of the ZIP drive is a bit bigger than a floppy connector, so what did he do? He kept pressing the cable onto the back of the Zip drive until the extra pins bent to the side!!!!!!!! He thought this would work!!! I could not believe it. I was like, "This is like legos, how could you not notice that the connectors were not even close to the same size?" And he says, "I didn't look, I just kept pushing it on there till it stopped." So I said, "I can't believe they let you have a gun AND a car."