Successfull iPC 10.5.6 installation on:

AMD64 Athlon X2 5000+ @ 2.80GHz
Northbridge: NVidia Quadro NVS210S GPU
Southbridge: NVidia nForce 430B MCP
4 Gb DDR2 800Mhz RAM
C-Media 8738 Audio
Realtek RTL8139 LAN
NVidia GeForce 6600 128Mb RAM
SATA II 500GB Samsung

But I went into a lot of trouble 'till things finally worked out good:

At first, the installation failed because the audio kexts from the DVD were corrupted.
Then, I tried once again, without installing the audio kexts. Installation went fine, but I saw the mouse pointer was moving extremly slow. Somehow, I've managed to delete the nvdarwin kext. The mouse pointer was now moving, but, without the video card injector, it was useless.
I accessed the Extensions folder to check out if the disabler was there. Well, there it was. But, I also found AppleCUPThermal.kext and AppleThermal.kext. I've deleted those kexts then reinstalled nvdarwin.
And now I have a fully functional 10.5.6 on my AMD computer. Oh joy!