Hi Thorazine. Thanks so much for posting this guide.
I've got the same motherboard and USB key as you..
gigabyte ga-73pvm-s2h
sandisk cruzer 8gb
bfg 9800GT
SATA hd

I'm having trouble booting the installer. I followed your steps, but when I choose my Mac OS X install disc in Chameleon, it starts loading up a few kexts, says "Loading Darwin x86".. and goes into a reboot loop. I've spent hours trying to figure this out... BIOS settings, command line switches (-f -x -v -s cpus=1), and nothing is working for me so far.

I've even tried installing the voodoo kernel, but it gets to the install screen (so, it does get further), and the kernel panics.

Any advice? The reboot loop really sucks.

EDIT: I forgot to note - I was using Leopard retail 10.5.1 .. I'm trying 10.5.6 now. Will update this thread if there are any changes.