I have finally managed to install Leopard, both 10.5 and 10.5.6 (using the 2 USB key Windows method). On both occasions, following installing the DellEFI, I receive 1 of 2 errors:
1) If I allow the Mini9 to boot normally, I receive an error stating: "You need to restart this computer" on a nice grey screen.
2) If I use my small USB key to access the boot loader and boot using the "-x" command, after the apple logo appears I see a blue screen which does not change (I have left this for 10-15 mins + and it still remains).
I first received this when installing 10.5 and thought it may have been a bad install but it happens after installing 10.5.6 as well. On both occasions I have used the DellEFI after booting into OSX. Unfortunately I am now unable to get back into OSX to rerun the DellEFI.