Dear Maintainer,
How to reproduce:
Put hardcopy Descent II CD in drive and mount it.
Mount your C drive.
Mount D: as your CD mountpoint, as type cdrom
Run installer.
It will say you have to have the CD in your drive, and install from CD.
I used DOSBox 0.74 on Windows, and it installed and ran just fine.
I suspect DOSBox is unable to see the audio CD tracks, or unable to
support copy protection (imaging the disk gave an I/O error)
Possible fix: Ability for DOSBox to mount raw CD devices and images.
Possible fix: Change system mount behavior to include audio CD tracks
under mount point (maybe with leading backslash on the filename, so no
possible confusion with another file), and adapt DOSBox to see them as
audio CD tracks.