Q: Difference between a PC and a Mac? 
Possible Duplicate:
Is it possible to install Mac OS X on customized hardware? 

Well I think the title is the main question here and aside from that:


*

*What is it that does not allow the MacOS to be installed on a normal PC ?

*How do I install the MacOS on a PC ?

A: Contrary to rumor, there's hardly any hardware difference anymore. Macs run Intel CPUs, nVidia/AMD GPUs and I believe Seagate HDDs. Pretty stock stuff.
There is a difference at the OS level and the BIOS (or equivalent) needs to be compatible with that. Things like EFI and GUID partition tables are the most notable low-level differences.

What is it that does not allow the MacOS to be installed on a normal PC ?

Depending on your PC, potentially nothing. The hardware may not be compatible, OS X is intended for a smaller range (since Apple has more control over what it goes on than other OSes). You may be able to find third-party drivers for common hardware, though.
