I found this out a while ago when looking for info on reading .DMG files on Windows or Linux boxes. I found out it was not possible, and I wasn't too happy. You see, my iMac has no CD-R drive, just a CD-ROM. This tip creates ISO images from DMG images, so they can be burned elsewhere. To convert the file to an ISO image, type the following command at your terminal window:
hdiutil convert /path/to/filename.dmg -format UDTO -o /path/to/savefile.iso
Replace /path/to/filename.dmg with the path and name of the existing .DMG file, and replace /path/to/savefile.iso with the desired path and name for the converted image.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20040121135301830