I'm using the exact same setup, XFX nForce 750a with AMD Phenom
I had to put my IDE DVD drive as master and then I could boot fine with some distros like iAtkos 10.5.7 and some others I forget. . .

The drivers you want to use are listed in this post:
http://www.insanelymac.com/forum/ind...owtopic=172553

just make sure your SATA settings in BIOS are set to AHCI

The drivers I'm using are:
Onboard LAN: Yukon88E8056
Onboard Sound: VoodooHDA
GeForce 7300GS: NVinject
HardDrives: ahci.pkg & genericata.pkg from iAtkos 10.5.7

note: I'm actually running retail now from a boot132 so I can update with no hassles. . .