Extra ring on the CD?
 

I've been trying to burn the recent release of Space Channel 5 part 2, with no luck. The cdi file burns fine, no errors at all. Same with the unzip. But the disc, for one reason or another, doesn't work.

I looked at the bottom of the disc, and saw something really weird. There is a ring of unwritten disc on the border where the Audio boot data seperates from the Game data. What exactly is this? And how do I get this game to work?

I'm not sure, but I think it's the gap between 1st and 2nd session. It happens sometimes.

You might try to remake your CD (extract all the files and use Bin2Boot, or something like that).