I had troubles using the registration string in MakeCD too, eventually I found out how to enter it, this works under OS4: you have to confirm every field with the Return key and all fields must be filled, then the "Save" button will appear.
Regarding Linux, there's still only the original Woody installer for A1, after that you'll have to upgrade your system the the more recent Etch version. Do you have the Debian Woody installation CDs? You should have also some space free on your hard drive to setup the dedicated partitions.
Varthall