What is a Disk Image? Why is it needed?
Disk Image is a mirror of your logical drive that is stored in one file.
This can be useful when you want to backup the contents of the whole drive, and restore it or work with it later.
Before you start recovering the deleted files, it may be a good idea to create a Disk Image for this drive, if you have enough space on another drive.
Why? Because if you do something wrong while recovering the files (for example, recovering them onto the same drive could destroy their contents), you still will be able to recover those deleted files and folders from the Disk Image that you have wisely created.