It's a kind of a hack but, but here is what you do (I found this online in a forum somewhere, I just don't remember where):
Install DVD Decrypter. Open (in separate windows) Img Burn folder and DVD Decrypter folder. Make a "Copy" (not shortcut) of the Img Burn application and paste it into the DVD Decrypter folder. Close Img Burn folder. Now add "(old)" to DVD Decrypter application to rename it. Then rename the "copy" of Img Burn to DVD Decrypter (make sure it is identical to the original DVD Decrypter application name or it wont work. Now run DVD Shrink like normal and when you make a back up of your DVD you will have the option of creating the ISO or ISO and burn with DVD Decrypter.
Have fun!
