I honestly don't know. How can I rename it? If you mean by just putting .iso at the end it doesn't work. Otherwise I have no clue.
I'd like to know the answer to this question as well. I have two disc images that are somegame-flt.cd1 and somegame-flt.cd2. I can't seem to do anything with them. I've tried using ISObuster on them and it opens them and converts them to .bin or .tao files, but I still can't do anything with them.