eMac won't boot from Crossfire external

[Glaskin]

I've installed OSX 10.3.9 on my SmartDisk Crossfire 160GB external FireWire drive and selected it in the Startup preference panel of my eMac (which is running 10.3.9)

Trouble is, it ignores my preference selection and always boots using the internal hard drive.

And when I hold down Option during startup it doesn't even find the external drive and its operating system files.

I'm running OSX 10.3.9 on my eMac and my CD drive is broken.

So can the Crossfire be used for booting or am I being utterly foolish in one way or another?

Glask