Install Leopard Via Flash Drive on PowerBook Problems

I put my Leopard install DVD (DVD drive is down) onto a flash drive to install on my 12" PowerBook G4 1.5ghz but when it restarts it just boots back into Tiger. I attempted to reboot and hold option but the only boot choice is the HD. Even if I go to Preferences>Startup Disk there's no option to boot from the Flash Drive.

The instructions I used to setup the flash drive with Leopard were from here: http://www.maciverse.com/install-os-x-snow-leopard-from-usb-flash-drive.html

Any help would be greatly appreciated!

 

Thanks, I actually stumbled upon that write up as well. Was hoping there was an easier route. Thanks though.