I'm trying to install Leopard on my G4 Mac Mini from USB. After poking around in OF mode I got the thing to boot off of the USB (a proper clone of my DVD). My happiness was soon shattered when I got past the Apple logo screen and a blue screen. I was presented with a grey screen and a 'beach ball'. I saw the USB usage indicator light was on so I left it for a few hours with no success. Any suggestions? I've reset the SMC and PRAM.