How to boot from my WD 1TB HD

[Turpentine]

I'm trying to figure out how to boot from my WD 1TB HD as my PowerBook G4's hard drive is toast. I have partitioned the WD DRIVE, and installed leopard. But computer still wants to boot from the internal drive. How do I get it to boot from the external? I tried the power then holding down option key and allthat came up was the broken internal drive. What am I doing wrong?

 

[BobZune]

Is this a Firewire drive? PowerPC Macs (like your PowerBook) only boot from (external) Firewire drives, not USB drives.