linux guy writes:
# fdisk /dev/sdb
Device contains neither a valid DOS partition table, nor Sun, SGI or
OSF disklabel
Building a new DOS disklabel with disk identifier 0xf7941c52.
Changes will remain in memory only, until you decide to write them.
After that, of course, the previous content won't be recoverable.
Warning: invalid flag 0x0000 of partition table 4 will be corrected by
w(rite)
Command (m for help): p
Disk /dev/sdb: 160.0 GB, 160041885696 bytes
255 heads, 63 sectors/track, 19457 cylinders, total 312581808 sectors
Units = sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0xf7941c52
Device Boot Start End Blocks Id System
Looks like the partition table took a hit. Unless you remember your
partition layout, you're pretty much done. The only thing you can do is
create a new partition table, format them, and make a fresh start.
But, at this point, I wouldn't trust the drive.