You could always create a bootable CD of Parted Magic.
http://partedmagic.com/doku.php
It's a Linux-based rescue environment. Just create a bootable and boot to it. This video talks about this process:
http://www.youtube.com/watch?v=yRWyjrh4Tcc
The big thing is to have some place to put the files after you retrieve them, and the video goes over this. What he refers to as "Windows files" should work for whatever you have for backups, provided the drive is detected. If you can't detect the drive, things get a lot harder, but I have been able to get files off of a disk that even Disk Management couldn't detect, so you should be fine.
Once you have the data off, you can start working on the drive. You could start in Parted Magic and try to format it and then see if you can find it in Disk Management in Windows, but I would try to just get the data someplace safe, boot to Windows, and see if you can find the drive in Disk Management before you start playing around with the drives.
I will warn you, be careful what you click on in Parted Magic and be doubly sure of what drive you are working on. A mix-up between your external and your boot disk can make for a long, long day.
Good luck, and feel free to hit me up if you need help. I'll be around.