Better yet...
Tell them to go into Open Firmware.. do a "devalias".. Look for "ud" prefix.. ud is what you need in order to set the boot variable to the USB device.. for example..
Say I have a USB flash drive with Leopard installer on it. I stick the usb flash drive into my USB port.. Go into open firmware and type in: "devalias" - seeing that this is present, I finally type in the following:
boot ud:,\\:tbxi - and away it goes!!! USB 2.0 booting is not that slow, but it does take a bit a second or two for the alias to point to the device(drive) and boot from it. If you have only ONE USB boot device, then the default: boot ud:,\\:tbxi works great.
If you read the article I linked to you'll see that all you are doing in OF is telling it to make an "alias" to the drive and then boot from the alias. It's non-volatile, you don't write anything to OF that won't be forgotten at the next book.
My caution was solely based on the fact that many Mac users are hesitant to poke around in OF except when resetting NVRAM is warranted.
Again, read the article and you'll see what I mean. The next restart after booting from USB and the Mac will have completely forgotten about the drive. Just exercise the usual due caution is all.
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What is also amazing is I did this same exact thing with Tiger 10.4 for my Pismo G4(Was G3 500). The difference is the USB ports are 1.1 ports, but what was strange is that when I hit OPTION key, the USB flash drive with Tiger shows up!, where as on the USB 2.0 PPC macs I have(G5 Quad, PowerBook G4 1.67 DLSD) it does not..
I can only think of one thing.. Apple restricted USB 2.0 booting from showing up in the Startup Manager, where as on the 1.1 USB PPC macs this does not seem to be a problem.
Or, is there a way to get the USB Flash drive to show up when one hits OPTION key to get to the Startup Manager?