Hello everyone :)

Any mac users around here ? I’m puzzled, with something potentially not entirely inside the usual scope of what one may call legality…
Advice from someone used to .dmg files would REALLY come in handy, please, pretty please :)

I have a 10 years old ibook G4, offered by a relation. PPC shit with 30 GB of disk, but it may serve as a multimedia box for my kids, in replacement of the dying Dell they currently have.
My own machine has a windows 7 OS.

I also have on my disk a “Mac OS X Install-Single Layer DVD.dmg” file (single layer, because I can’t burn double layer ones) with the latest OS possible to install on this crappy machine, I think this is Leopard. I DO want to update the 10-year-old OS of the notebook, one hour trying using Mac was enough to make me want to install an upgrade over that unfriendly shit.
I burnt the .dmg file with PowerIso, with success, it verified the compilation and found it to be perfect.
The Mac only recognizes a disk is inserted in the slot named like that, but won’t manage to open the goddamn disk or read its contents.

I also have a yellowdown linux 6.2 DVD successfully burned, with verification, by Burn-Aware from its official .iso file. This one, the Ibook g4 manages to recognize it and fully browse its contents.
However, it won’t acknowledge it as a bootable device, hitting Alt on startup only shows the hard disk as the single bootable device.

I desperately tried the C key on startup, but as verifying with the Alt key showed, no, none of these disks are bootable disks for this Mac.
Also tried with an USB external DVD reader, same deal.

I can’t put the .dmg file on an i-shit-something like an ipod, I don’t have any.
I can’t put the .dmg file on an HFS+ formatted USB key, it’s larger (4.3 GB) than my largest USB key (3.7 actual GB).

Sooo… What the fuck, lol.
I gave up on asking on Mac forums, they are apparently full of imbeciles confusing software with religion and they can’t tolerate that one may not wish to actually buy an OS for a 10 year old machine that’ll serve as a divx player, and they entirely discard Linux installation attempts.

Would you know where I have gone wrong, and why neither of the DVDs supposed to be bootable, are bootable ?

Thank you SO MUCH if you can help ! ^_^