It's rather dangerous to repair disk partitions on a corrupted hard disk drive. You can even apply 1 of the greatest data recovery tools and be sure in your actions, you are still risking to waste your files. Changes made to the damaged partition are irreversible; it is too simple to destroy an important system structure containing vital information about your disk, files and data. Bottom line: it's good to backup before making data recovery. Or is it?
You can find the other way of data recovery process that may be even more harmless and simpler and it does not demand to have substitute. Instead of making a backup copy of damaged files, you can simply make a complete double image of the disk or partition being repaired, and try the fixing with diverse settings as many times as you require on this snapshot instead of the actual disk. This is one of the possibilities of data recovery software.