Floopy cables can be put in upside down.  If your floppy drive light stays on all the time you got the cable reversed.  It may still read but it will destroy the boot sector.  Otherwise make sure the drive works at all.  Sometimes after it shows a problem once the problem stays but since it didn't change you won't see another error until something else changes.  If you can read floopy's and your light doesn't stay on all the time you'll be fine.