The drive workrd at some point.
When did it last work?
Have you installed anything recently?
Have you opened your box in recently (to add hardware, clean it, etc.)?
Is the Floppy Drive light on constantly?
Does the light come on at all?
What happens when you try to access the Floppy Drive (A:) without a floppy in it?
Have you tried booting with a floppy in the drive (to see if the BIOS properly detects the drive)?
Have you made changes recently to your BIOS?