We can backup a CD to a new CD-RW just like backup to a CD-R.
However, if a CD-RW has been used several times and then formatted, a CD can NOT backup to this formatted
CD-RW. Why? Theoretically, a CD-RW is re-writable, so we can theoratically recover a CD-RW to an as-received
state just like a new CD-RW. Why not? How?