I am guessing that there is not really a floppy in the drive and the computer is looking for one at shutdown? Hence the noise.
Try putting a blank floppy in the drive next time before shutdown.
If there is a floppy in the drive try taking it out before shutdown.
My laptop does not have an inbuilt floppy drive but I seem to vaguely remember this problem at college where we had to save work to a floppy. If I took the disk out before shutdown the computer would start looking for one during shutdown, because although I had finished saving work the program was still open when I shut the computer down.
Wiliam
