From this post from robbieduncan at macrumors:
- Open Disk Utility and use the New Image from Folder menu item to create an image. Ensure it is uncompressed and use the CD/DVD master option.In my experience this creates HFS+ masters which are no good in Windows.
- Open the Terminal
- Assuming your new image is called ~/Desktop/Master.cdr (the file is on your desktop and called Master.cdr) type:
cd ~/Desktop hdiutil makehybrid -iso -joliet -o Master.iso Master.cdr
This will create an ISO/Joliet .iso file.