TestDisk is a powerful free data recovery software that can recover lost partitions, fix partition tables, and undelete files from various file systems including FAT, NTFS, and ext2. It can run on multiple operating systems including DOS, Windows, Linux, and MacOS X. The software is open-source and licensed under the GNU General Public License (GPL v2+). TestDisk is designed to help recover data from faulty software, viruses, or human error. It provides features for both novice and expert users, allowing them to collect detailed information about non-booting drives and perform onsite recovery. The software can fix partition tables, recover deleted partitions, rebuild boot sectors, and fix file tables. It can also undelete files from FAT, exFAT, NTFS, and ext2 file systems, and copy files from deleted partitions.