The only thing I can think of is to boot into Linux (maybe using Knoppix?) and see if you can mount it as UDF and/or ISO9660.

To be honest, I don't know for sure that Linux implements separate filesystem drivers for them, but I think it does, and if it does, a simple ``mount'' should show you what filesystem it's mounted as, if it mounts automatically, or you could try to mount it manually specifying each fs type (I think you can have hybrid ISO/UDF discs).