Can't install OSX on external firewire

[David L. Olson]

I just added an external firewire drive (Western Digital 100gig) in an
inexpensive firewire enclosure and when I try and install OSX on it the
installer won't allow it. I'm not at home, and can't recall the exact
dialogue, but the drive had something drawn through it in red on the screen
where you choose the destination drive, and the message was to the effect it
was not supported on this computer. The drive jumpers are set to master, I'm
running the 10.2 installer disk, stock cube with 384 mb of ram. What am I
doing wrong?

TIA,

David Olson