Mac Pro :: Backup / Retrieve Files From An External Hard Drive That Doesn't Appear In Devices?

How would I go about backing-up the disk if the image doesn't appear under devices? I went to the "Restore" tab/button, but I can not choose the hard drive in the first field. I could have sworn my hard drive was formatted for Mac, but I may have formatted it back to FAT32. I know the disk still functions because when it is powered on, it cycles with/without being connected to my MacPro, but after that, it will only cycle if connected (confirming connection). It does run again when I connect the firewire cable. Here is my equipment: 8-Core MacPro 16GB-Mem RAIDMacOSX 10.6.8 | 2 X 1TB Internal HDD&Aug-2008 15" MacBookPro(That I used the Maxtor-External with mostly) DEVICE IN QUESTION500GB Maxtor One-Touch PlusFireWire 400 6-pin Connection Bus (2 Ports)Purchased in Early 2008 from Staples I can fit the back-up on my 2nd HDD in my MacPro or in my other External: 2 TB G-Technology G-RAID External1 x eSATA |  2 x FireWire 800 9-pin |  1 x USB 2.0Self Powered DC-IN  I have had a nightmare searching for answers, so any options you might have would be tremendously helpful. I can't lose the data because I have everything I did during film school on there. That stuff is basically what you pay for when you go to film school, you pay to show what you can do and what equipment you have used.

Info:
Mac Pro, Mac OS X (10.6.8), 2x2.4GHzQuadCore 16GB-Mem 2x1TB HDD