What is a disc with unsupported format

It's a CD with a file system, and/or data pattern that can't be read by Windows or MS DOS.

It can also be a home-made CD that did not burn to the disk correctly.

There is nothing that can be done, what it is, is what it is.

There is no way to fix anything with the info you provided, what disk are you trying to play and what should be on it? Where did you get the disk? Is it a disk made for Windows?