I have read quite a few forum pages and blog posts on this but could not get it to work. I thought the best I could do was to sum up my experiments here and try to get comments to help me.
Hardware

So, I understand a big part of this installation is to have a computer that matches the compatibility list. I had read that list when I built my desktop and I believe OS X can be installed on my computer.

* Motherboard: Asus P5K
* Processor: Intel Core 2 Duo E6750 2.66 Ghz
* Ram: GSkill 4Gb
* Video: NVidia EN8400 GeForce 256Mb
* Ethernet: built on board, Attansic L1
* Audio: built on board, Realtek

BIOS

From what I understood, OS X can only boot if it is able to detect the DVD Drive and the Hard drive at boot up. I tried several configurations but the only one that enabled me to boot from Leopard Disk and boot the installed OS is as follows:

Main > System Information > Asus Bios > Version > 0704

Main > System Information > Asus Bios > Build Data > 10/30/07

Main > SATA Configuration > Compatible

Main > SATA Configuration > Configure SATA as IDE

Advanced > OnBoard Device Configuration > J-Micron eSATA/PATA Controller > Enabled

Advanced > OnBoard Device Configuration > Controller Mode > AHCI

Power > ACPI Version > Disabled

Power > ACPI APIC Support > Disabled

I fiddled a lot with these settings after installing the first distrib I tried in order to boot Mac OS X with Super Grub disk. That never worked. These are the settings that allowed me to boot iDeneb, though. Changing the SATA configuration broke my ability to boot the iDeneb distro DVD (even though these settings are not what are recommended on this post: The OSx86 Scene Forums • View topic - [Guide] ASUS P5K Vanilla(Plain): Installing Leopard [080111] ! When I followed the one on the post cited, it wouldn't boot the iDeneb DVD at all)
Distrib

I tried several:

1. Atkos v7: I could install it but never found a way to boot it. After suceeding with iDeneb, I think I could have succeeding in booting that one, too. If someone believes this is the right distrib for my hardware, I will try it again.
2. iDeneb (iDeneb_v1.5.1_OSX86_v10.5.7): This is the one I managed to install and boot by starting with the disk in the drive and pressing F8 when prompted and then typing rd=disk0s2.
3. Snow OS X (SnowOSX_Universal_10.6(432)GM_v3.5): On start up, it displays the message "press any key to boot from disk or F8 to enter option" but whether I press enter or not, it doesn't boot from the DVD but from the hard drive. I could not install it.

Installing iDeneb

When installing iDeneb, I first used Disk Utility in order to format the hard drive creating 2 partition using a GUID partition system. The first partition is 200 Gb and is named Mac OS X. The second is 300Gb and is called Data. They are both formatted as Mac OS X (Journaled)

During the installation, I clicked on customize and selected the following to be installed:

* Fix > AppleSMBIOS > AppleSMBIOS Patched > AppleSMBIOS 800 667 Mhz
* Fix > IOUSBFamilyFix
* Drivers > Audio > ALC Audio > ALC883
* Chipset > ICHx Fixed
* Chipset > JMicron ATA
* Network > Ethernet > Attansic L1
* Video > NVidia > NVDarwin 256Mb

Current Situation

The current situation is that iDeneb is installed but

1. the computer doesn't boot on its own, I need the leopard disk, press F8 and type rd=disk0s2
2. several components don't work (ethernet/graphic card)

Ultimate Goal (triple boot)

My goal is to have a running OS X with video card, audio and Internet ;-) Obvious, I know.

I would also like to put my old main hard drive back in the computer. The old hard drive has a running Windows XP and a running Ubuntu installed. Grub is handling the bual boot. I would like, in the end, to use Grub to boot Windows, Linux or OSX.

Try adding EFI strings using EFi studio or OSX86 tools to get QE/CI support, audio dont work? are you sure thats your audio chipset? try with voodooHDA, Lan doesnt work? did you check any guide for this mobo?

i think i read your post right. so it wont boot up after the install? if thats what im reading. well i had to use ihack with empire efi post install. which i think is a version of chamilion (<--- not spelled right )if im not mistaken. and it basically makes it boot to the os. if i read it wrong im sorry. im having osx problems of my own right now lol