The source for this article was: http://support.apple.com/specs/
Pick the Hardware specs on the right hand side for the model to
see a reverse chronological listing of model releases. The model numbers given below are in chronological order. Anything released as newer not stated here can boot into 10.5 as of the date of this article. As of the writing of this article it has not been noted which new Macs won't be able to boot into 10.5 retail. Since that would be speculation at this point, that is not given here. Some models below do not come with a DVD drive, though some Firewire drives should potentially be able to boot Leopard. Consult with the Firewire DVD drive manufacturer after October 26th, 2007 to find out if yours does.
According to http://www.apple.com/macosx/techspecs/ these Macs are excluded:
All G3 Macs.
G4 Macs up through 800 Mhz including:
iMacs models M8672LL/B, M7677LL/B, M8535LL/B, M8812LL/A, M9105LL/A
iBook model M9164LL/A
PowerMac G4s with graphite (looks like dark blue), Cubes, and QuickSilver models M8359LL/A, M8361LL/A, M8705LL/A
Powerbook models M7952LL/A, M7710LL/A, Gigabit ethernet, M8591LL/A, M8592LL/A
eMac models: M8577LL/A, M9150LL/A
Original Mac Minis with 2 USB ports, while not excluded by the Mhz rating require an authorized service center to install memory to bring it up to the necessary 512MB of RAM, or being technically skilled with a putty knife and not damaging the interior equipment, which could completely disable your equipment entirely.
The G4s capable of booting into 10.5 are:
iMacs: M8935LL/A, M8935LL/A, M9285LL/A, M9168LL/A, M9290LL/A
eMacs: M8950LL/A, M8951LL/A, M9425LL/A, M9461LL/A, M99832, M99833, M99834, M9835
iBooks: M9426LL/A, M9418LL/A, M9419LL/A, M9388LL/A, M9165LL/A, M9623LL/A, M9627LL/A, M9628LL/A, M9846LL/A, M9848LL/A
PowerMac G4 QuickSilver models: M8360LL/A, M8666LL/A, M8667LL/A; Mirror Dual drive models, Firewire 800 models.
Powerbook G4: M8858LL/A, M8859LL/A, 12", 17", 15" with Firewire ports on the left or right side when the keyboard is facing you.
Naturally all G5 and Intel Macs are capable of installing Mac OS X 10.5.
Notes: When a specific standard is noted in a name of a model, that's the name given to the original Mac released with that standard, as given by:
Such as Powerbook G4 Gigabit ethernet.
That does not mean all models with Gigabit ethernet fall in that classification, only the original release.
Some models with the same classification fall in both categories of being
able to boot into 10.5 and not being able to such as the PowerMac G4 QuickSilver. For those models both the descriptive title and the model name is given.
If your computer has less than 512MB RAM, you would need to upgrade to at least 512MB.