Penguin

Wrong Medium Type

You put a floppy disk into your CD-ROM drive.

Seriously, this error means that a device driver couldn't understand the currently connected media. For example, you have tried to mount an audio CD as a data disc, or alternatively tried to listen to a data disc as a music disc.

The linux kernel also uses this the atmtcp network driver, and in some tape and disk drivers when running on the IBM s390 architecture.