There are many softwares that offer unformat and undelete features in case you need to retrieve your old data back in your hard disk. I tried quite a number of them and many of them did not consistently retrieve my binary files. Sure, text files are very easy to retrieve but I noticed that large binary files posed a problem for these undelete softwares.
I did try one. It is called ReclaiMe. This software recovers various media hard drives both internal and/or external, memory cards used in cameras, mobile phones, PDAs, MP3 players and USB drives. It is very simple to use, any non techie person can easily use the software. You can preview the recovered data even before the recovery is finished.
There is no need on how to unformat a hard drive. All it takes is a few clicks with ReclaiMe and it does the rest. It is a data recovery software for all occasions.