How to convert your commercial DVD discs to .iso format
(for duplicating non protected DVD instructions, visit this page)
Begin by downloading MacTheRipper, a freeware DVD copy utility. You will use this program to duplicate your commercial DVDs onto your hard drive.
Once you open MacTheRipper, it will detect the DVD in the drive and prescan it. You'll need to select a location to save the disk copy to, and also select a Region (it will warn you if you select a Region that is not possible). Generally, setting it to "OFF" works.
Once the DVD is copied, you may quit MacTheRipper.
Open Disk Utility (Applications/Utilities/Disk Utility).
In Disk Utility, click the file menu and pull down to the new --> Blank Disk Image.
The New Blank Image dialog box will appear. Name the file (Save As:), where to save it, and change the size to 4.7 GB (DVD-R/DVD-RAM) or 8.0GB (DVD+R DL) depending on the size of the DVD you just extracted . Click Create.
The disk image will begin creating. It does not take as long as shown above. :>
Locate the copy of the DVD that you made with MacTheRipper. Copy the folder (or folders) that it created onto the disk image that you just made. If the disk image did not mount, find it where you chose to save it, and double click on it - it will mount, remember, it's a read/write disk image.
The file structure should be at least one folder, named "VIDEO_TS". There can be other folders in there, but that is the important one.
Mac OS X will confirm that you want to do this change. You most certainly do want to. :>)