Passport 730 not recognized

Any solutions found for the masses of passports showing up as unrecognized. Plugged mine in to Windows 7, Vista, XP, and they all have it show up in the computer management but without a drive letter. Can’t assign a drive letter to it to access data. No I can’t reformat it as it is my backup and it is my only back up. Any ideas? 

In Disk Management does it say anything like Raw or Unallocated? Have you tried a different USB cable?