Floppy drives are a thing of the past. However, the people at SophosLabs, love computer history so much that we have to have floppy drives around. Floppy drives can do more than they were originally designed for. Floppy drives can help tell you that your computer is infected sometimes.
The above video is from a floppy drive on a computer infected with W32/Xanib-A.
Certain worms / virus will poll removable drives to infect and thus when the floppy drive is making frequent noise when it shouldn't be, there might be a chance you might be infected. Floppy drives do make noise when they are in pain ;)