This article is from the CD-Recordable FAQ, by Andy McFadden (email@example.com) with numerous contributions by others.
If the disc was created with a packet writing program (like DirectCD
or HP DLA), it will either be in UDF or ISO-9660 Level 3 format. Either
way, you're not going to be able to see files on the disc from DOS.
You need to use a more modern OS, such as Windows or Linux, or create
the disc with a conventional premastering application like Nero.
Some backup programs, such as Symantec Ghost, use packet writing when
backing up to CD-R. The software runs under DOS, but uses a special driver
to create and access the backup data. You can see the files from Windows,
but won't be able to get at them from DOS.