mac pro

Everytime I try to change my system definition off mac pro 3,1 my ML partition wont boot anymore. I want to change it to the new imac so I can get native airplay without using airparrot. Anyone have any ideas why as soon as I change it I cannot boot anymore? Thanks in advance! specs...

I am one of the curious ones out there. But, I couldn't help but wonder if there would be a way to get Mountain Lion on my MacPro 1,1 providing I get a GPU from a 2010 model MacPro so it does not stop at the 64bit GPU check. My guess is one could customize a Unibeast install enough to make it...