This is problem with the older versions of the Apple CD-ROM driver. However, if you install CD-ROM Setup 5.1.5, you will be able to mount both partitions. Of course, this runs into the problem of needing a CD-ROM disc in the drive at startup in order for the PC to use the drive (assuming you have the DOS Compatibility Card installed). If you are not familiar with this problem, it is documented in the Tech Library article titled "DOS Compatible: CD-ROM Needs to be in Drive at Startup".
Version 1.5 of the DOS Compatibility software installs CD-ROM Setup 5.1.6 and also corrects the problem mentioned above.
The steps required to see the DOS/Windows partition are:
Step 1
------
Insert the hybrid CD-ROM into the drive (just so the CD-ROM is in at
restart).
Step 2
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Install CD-ROM Setup 5.1.5 and restart.
You should now be able to see the PC partition on the PC and the Macintosh partition on the Macintosh.