*Before you start, if you have important data you definately need to recover, then first make a backup of the partitions (or if unsure of the whole disk) to another medium or another drive. if you don't want to use a proprietary solution, or Partimage, then just do "dd if /dev/hdbX of=/mnt/anotherharddisk/somefileX" (where X is a partition number) .
"fdisk -l /dev/hdb" should show the partition table.
If you don't recognize any of it, or if it shows plain wrong info, try testing your disk (and recovering your partition table if necessary) with
Testdisk and
Gpart.
If it does show a correct partition table, then "mke2fs -n /dev/hdbX" should give you the locations where the backup superblocks are. Run "e2fsck -b <backupsuperblock> -n /dev/hdbX" for a testdrive (answers "no" to all questions and nothing will be changed) if you need to see what e2fsck will be doing before it actually does it. Now run "e2fsck -b <backupsuperblock> -c /dev/hdbX".