Make external hard drive bootable from ISO image

[convict]

Not strictly Fedora-specific I suppose, but I need to boot a live CD on machine without a working optical drive. I already considered unetbootin - however, my external hard drive doesn't show up there (it's not under HDD nor USB). I know I could just use a USB key, but I'd rather learn to make external hard drives run live distros (this isn't the first time I have a need to do something similar). None of the guides I've found so far are very specific as to what to do, and my several attempts so far have been unsuccessful.

Where would I begin?

[JEO]

Typically external usb hard drives come formatted with ntfs which is nice for file sharing but not very good for live usb booting. If you don't already have important data on it you could repartition it with about a 4GB vfat fat32 partition in the first primary partition so it can be easily made bootable (the same file system that 4GB usb flash drives come witih). Then you could run the liveusb creator program or livecd-iso-to-disk script to create your live usb in the usual way.

[convict]

It's already formatted as FAT32 (the entire drive). I'll take a look at this liveusb-creator though - thanks for that.