TestDisk is a powerful free data recovery program! 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 your Partition Table).

TestDisk can find lost partitions for all of these file systems:

BeFS ( BeOS )
BSD disklabel ( FreeBSD/OpenBSD/NetBSD )
CramFS, Compressed File System
DOS/Windows FAT12, FAT16 and FAT32
HFS and HFS+, Hierarchical File System
JFS, IBM's Journaled File System
Linux Ext2 and Ext3
Linux Raid
RAID 1: mirroring
RAID 4: striped array with parity device
RAID 5: striped array with distributed parity information
RAID 6: striped array with distributed dual redundancy information
Linux Swap (versions 1 and 2)
LVM and LVM2, Linux Logical Volume Manager
Mac partition map
Novell Storage Services NSS
NTFS ( Windows NT/2K/XP/2003/Vista )
ReiserFS 3.5, 3.6 and 4
Sun Solaris i386 disklabel
Unix File System UFS and UFS2 (Sun/BSD/...)
XFS, SGI's Journaled File System