Why would one ever need to recover data from an ISO image? ISO images are used to create CDs and DVDs. They are usually general file information as well as applications. Very often ISO image files are used to copy entire hard drives for security and backup purposes. When an ISO image file is damaged it prevents that image from being burned onto a CD or DVD. And as these programs were meant to run from disks, a damaged ISO file equals a non usable program. There are programs specific to ISO image recovery. These will scan the entire image file and translate the data it contains from the unreadable version to readable information.
Some of the better data recovery programs will actually allow you to access the information on an ISO file and then recover data from ISO image files that have been damaged. This amounts to the combination of two very difficult processes into one effective program.