songbird, main problem with CD-checks that they seeks for something particular. It could be certain "obsolete" file, certain order of tracks, "obsolete" bytes in "unused" part of disc or simply name of CD. And it is obviously missed from your custom-made CD.
I think, it could be guessed/hacked from main exe, but as there is "legit" CD-image exist, it's much simpler to take it and look inside.
I am still in process of downloading it, so I will say when I'll check it.
---addition---
Oops. It is DOS-version, and it is home-made disk too.
Pity.
Anyway, it's working.
It must not, but it is!
I investigated an issue. As I suspected, it's a simply CD-audio. Remove "music" check from menu at top, and issue will disappears for you too.