Thanks for the answers. Since I posted my question I got quite a bit further, same trial and error method you referred to
Anyway, what I have now is this:
3 partitions on a 500GB drive:
- EFI reformatted to HFS+ with Chameleon 2.0RC1 on it => ~200MB
- Mac OS X with iDeneb 1.3 install upgraded to 10.5.6 and most things working (ethernet, web cam, sleep, screen resolution, but not WiFi (although after I put the WiFi card from my AppleTV in, it works, of course) and not sound (yet)) => ~410GB
- another HFS+ partition of precisely 64GB in size. I use this to store installers, etc. while I'm at risk having to re-install Mac OS X from scratch. Eventually I will dd the 64GB partition from the original 160GB drive (I shrank the XP partition down to precisely 64 GB before), and hopefully Chameleon will then recognize that as a bootable XP partition, but time will tell. Windows is the lowest of my priorities.
In other words, my system is workable, but it's not "clean", which means I would like to have a vanilla install on the OSX partition and any required driver mods, etc. on the reformatted EFI partition, such that I can upgrade the system safely and don't have to wait for some hacked up upgrade package to show up (or not).
To test vanilla bootability i dittoed an original Mac OS X 10.5.6 install DVD onto the 64GB partition. That works because ditto won't delete other files/folders unless there's a collision, so all my hacking tools I have in a separate folder. Chameleon also lets me boot from this partition now, but unfortunately the boot won't complete successfully.
In other words, I need more/different stuff in my Extras/Extensions folder on the EFI partition. Hopefully it's just a matter of time until I figure out what, because once I can safely boot that DVD disk copied to a partition, I should also be able to boot a regular install. Once the former works I can do an archive&install of the vanilla OS onto the iDeneb partition, and if all works, I can delete the "Previous Systems" folder and have a full vanilla install.
Hopefully that will happen sometimes soon, because I rather use computers than hack them