Sorry to resurrect an "old" post, but I have a similar problem and a VERY similar computer that I'm trying to install Mac OS X to.
Mine's a ThinkCenter M55, but with a Core2Duo E6600 (@2.4GHz) CPU and I have a GeForce GT240 graphics card in it. (also the integrated Intel, which can't be disabled.)
So, my question is, is this computer compatible with 10.9 (or 10.8/10.7) at all, or am I just trying in vain?
I've tried various installer images on an USB stick but none of those will boot further than a few seconds (they hang after PCI init, so that I need to manually pull the cord, nothing will happen after that.)
I haven't (yet, downloading) tried any Niresh releases, but...
Are there some essential settings in BIOS that I really should change or do I need something special to get this to boot at all.
I do have a Mac mini (2006) that I can use as a "real" Mac if need be, but as it is a 32bit machine, no Unibeast or similar, unfortunately.