I'm having trouble making a Mandrake Boot floppy. But when I run 'mkbootdisk' I get the folowing error:

[root@jrb2 jrbishop]# mkbootdisk -v --device /dev/fd0 2.4.21-0.13mdk
Insert a disk in /dev/fd0. Any information on the disk will be lost.
Press to continue or ^C to abort:
Formatting /dev/fd0... mkdosfs: /dev/fd0 contains a mounted file system.
Failed to format /dev/fd0

what am I doing wrong and how can I fix it? I'm using Mandrake 9.1