Here's what I did:
1 I needed a new computer, so I bought all the new parts based on X86 specs (google hackintosh x86 they have forums there)
2. bought and installed OSX (installed thru multiboot)
3. bought and installed Win7 64 on a seperate drive
Process:
Select which drive to boot to, Boot OSX... you are then running a mac as far as anyone knows. Install all OSX updates, Xcode, iTunes, etc...
The upside of this process is that my computer is REALLY FAST. I think it's in the range of a $2500 MacPro, it cost me about $800, and runs Win7 when I want. Kinda 2 machines in one.
You can do this with almost any hardware, just gotta find the files specific to the bios, chipset, sound cards, etc...
You'll find a list of compatable parts at the forums and X86 Wiki site.
here's just one forum spot:
http://www.tonymacx86.com/index.php