For those that want to know how to format an unmountable encrypted PS3 hard drive via a USB to SATA enclosure using Linux:
1. Hook up the enclosure to your computer via USB.
2. Open a terminal and type
(should return external drive info)
3. Then type
(should return the location of the external drive, which in my case was /dev/sdb)
4. Then format the (unmounted!) external drive by typing
mkfs.msdos /dev/sdb -I
(note: your location will vary)
5. After formating is complete, unplug and plug in the USB enclosure. Linux, XP, OSX, etc should now be able to detect it as a FAT32 formated hard drive.