TestDisk is an open-source data recovery software that can run under:
Windows (NT4, 2000, XP, 2003)
FreeBSD, NetBSD, OpenBSD
TestDisk can help you recover lost partitions and make non-booting disks bootable again. It works with the following partitions: FAT12, FAT16, FAT32, Linux (EXT2/EXT3/JFS/RFS/XFS), Linux swap (version 1 and 2), NTFS (Windows), BeFS (BeOS), UFS (BSD), and Netware.