A friend who works in a college as an IT support recently had the same problem. The fixing of this problem lead to him getting a nasty gash on the chin.
A floppy on one of the computers didn't work. Simple, eh?
He put another one in.
Still no joy. Looked in the BIOS just to check noone had played around with any settings. No problem there.
Tried another lead. No joy.
checked any loose connections . No joy.
Took out various bits to try them out on other computers. No joy.
After about 4 hours fiddling about. He tried the original floppy on another computer just to make sure. [The poor fella said by now he was sweating badly, and panicking.]
No joy.
He thought just in case [haven't I already done this, but I'll do it again just to make sure] to try the new floppy in another computer.
There was the problem.
The new floppy was dead as well.
He got a third floppy, computer booted up. No problems at all.
He threw the floppy onto the floor, [and I didn't believe this, but the proof is on the chin] and it bounced back and hit him on the bottom of the chin.
So be careful young jabronie185