[Japo]

Are you sure your CD drive in Windows is D:? For example mine is E:, so I would use "mount d e:\ -t cdrom"

Besides possible authenticity checks, or even if the game does none, it's possible that while burning the CD you used a newer file system that DOS can't support. I think DOS supported only ISO9660, not Joliet or UDF. I think the choice of file system is included in an image file, but if you simply burned the files as Scatty says, the burning program may have defaulted to a more current file system.