DO NOT USE NORTON UTILITIES!!!
NU will cause more problems for you than what you are having now. I'm hoping that you haven't used it yet.
If you need a good utilities program, get DiskWarrior.
As for options, have you tried removing the drive from the Firewire enclosure and see if you can add it internally to a Power Mac tower or some other Mac?
Before you do any of this, you might want to try mounting it with Disk Utility and see if that works. You might be able to run a disk check on it from there depending on the filesystem type of the external drive.
• Apple iMac G5 17" (2 GHz G5) - Mac OS X 10.5.8/Ubuntu 10.04
• Asus Eee PC 901 (1.6 GHz Atom N270) - Fedora 13
• Apple Macintosh Quadra 650 (33 MHz MC68040) - Mac OS 8.1
• "JHVH-1" (2 GHz AMD Athlon XP 2400+) - Slackware 13.1