Fixing a broken hard drive's partition map
Have you tried asking disk utility to redo the partition map? Click on the disk, go into the "partition" tab, set it from "Current" to "1 Partition", click "Options", change the partition table to anything else, then repeat the process and set it back. If the issue is the partition table, that will fix it. If the issue is the drive, then it won't. Either way, you'll have your answer.