Holy thread necromancy, Batman! I presume in the nearly five years since this question was asked, the OP has addressed the problem somehow.
Old versions of OS X were designed to run on completely different CPU architecture -- PPC, not Intel -- and so can't be emulated. Rosetta, which allows PPC apps to run on Intel, requires an Intel OS underneath it, and only works for apps, not for the deep OS components. Finally, earlier versions of OS X don't have the drivers for newer hardware.
But my first question is really: why would you want to? If it's just to run some app, I'm sure there's an alternative.