http://blog.raxco.com/2012/10/31/the-danger-of-using-free-file-recovery-programs/
PerfectFileRecovery can also find traces of missing files that may have lost their file names. Most other file recovery programs (free and paid) cannot search for files that no longer have their “Saved As” names associated with them. If you search for missing files using PerfectFileRecovery and you don’t see the name of the file you’re looking for, it may be found under the name “Discovered_” followed by a number.
You can sort these files by file type or date to narrow down your search.
Finally, after a power outage or power surge, you may also run into corrupt drive issues. While most other programs (paid and free) cannot function properly on drives that have been corrupted, PerfectFileRecovery can retrieve lost files from corrupt drives – both physical and virtual.