TestDisk is OpenSource software and is licensed under the terms of the GNU General Public License (GPL v2+).

TestDisk is powerful free data recovery software! It was primarily designed to help recover lost partitions and/or make non-booting disks bootable again when these symptoms are caused by faulty software: certain types of viruses or human error (such as accidentally deleting a Partition Table). Partition table recovery using TestDisk is really easy.

TestDisk can

Fix partition table, recover deleted partition
Recover FAT32 boot sector from its backup
Rebuild FAT12/FAT16/FAT32 boot sector
Fix FAT tables
Rebuild NTFS boot sector
Recover NTFS boot sector from its backup
Fix MFT using MFT mirror
Locate ext2/ext3/ext4 Backup SuperBlock
Undelete files from FAT, exFAT, NTFS and ext2 filesystem
Copy files from deleted FAT, exFAT, NTFS and ext2/ext3/ext4 partitions.
TestDisk has features for both novices and experts. For those who know little or nothing about data recovery techniques, TestDisk can be used to collect detailed information about a non-booting drive which can then be sent to a tech for further analysis. Those more familiar with such procedures should find TestDisk a handy tool in performing onsite recovery.