First and foremost - you've done a fair job listing your hardware BUT you'll still need to list your EXACT sound codec (eg. Realtek ALC850) & your EXACT LAN chip (eg Realtek RTL8201 PHY) & etc. I'm assuming you've got nvidia 61x0 onboard graphics (which will work but not fully with QE/CI support I don't think...) The LAN chip will be important Once you're booting into the OS and for Initial Setup. If you're not sure the LAN adapter is 100% supported, DISABLE it in the BIOS until you're booting into the Desktop with no problems.
The Zephyroth Wiki will be your friend:

http://osx86.wikidot.com/

OK, BACK to your initial problem:

When the Installer fails to make your OSx86 partition bootable:
Restart booting off the Installation DVD
After the "boot options countdown" Press F8
At the prompt enter: -s & hit Enter (this boots from the DVD into single user mode)
when it all settles down and ends at the command prompt:

(here you'll be entering the "fdisk utility" to select your OSx86 drive and partition and make them bootable)
TYPE:
fdisk -e /dev/rdiskX ( hit Enter - replace "X" with your ACTUAL drive number ( eg. single HD will be rdisk0 ))
update ( hit Enter - updates MBR machine code )
f X (hit Enter - replace "X" with the ACTUAL partition number ( first partition will be "1" ) makes partition active )
w (hit Enter - writes the updated MBR to the selected drive and active partition - you may also need to enter Y here )
q (hit Enter - quits, saving changes )
reboot (hit Enter - restarts you computer )

When it restarts, boot (or try) from the HD. You'll get the Darwin Boot.... again and another countdown -
Press any key (to "enter startup options)
at the prompt type "-x" hit Enter - to start in "safe mode" else you'll have a "kernal panic" halt

Once you're in the Desktop, you'll need to delete several nvidia ".kexts" in the System/Library/Extensions folder. These are described at the Wiki:

http://osx86.wikidot.com/known-issues#toc1

( I don't use the method described there but it does list the files you need to dispose of: All "geforce*.kext" and all the "nv*.kext" files )

Move all those files to the Trash and then Empty the Trash bin. You can restart now and boot into the OS normally. Then you can go about installing the "real" .kexts for your video card and anything else that isn't working yet.

---

Running both 10.5.8 and 10.6.4 on my stinking AMD/ATi machine...