Adding in a gtx 460 2gb in a 2008 (3.1) MacPro?

I have 2 drives in my mac pro 4,1 so I installed windows on the second. OSX on the first. After I had finished installing windows I went back to OSX to fool around and make sure everything worked, which it did. Then I installed the newest nvidia drivers, and plugged in my gtx 470 as is described above. Go into windows, everything works fine, card is fast, gt 120 still running the monitor.

So I try to boot back into OSX and notice the bootloader skips it, going right for the windows drive. So I option boot OSX and grey apple screen I just get a blue screen. So I pop in my 10.6 disk, and option boot the dvd, same story. Anyone have any suggestions? Apple won't really talk to me since its unsupported stuff. Help would be appreciated.

(side note: the 470 seems quiet, doesn't make much noise at all, not even while running at 20 gigaflops/sec with octane render (which seems like it would constitute "underload", seems hot in the back but that's what everyone says about it. Is there any way to monitor the fan, and make sure it is spinning up? And that I can't just hear the gt 120?).