What do you want to do?
Install a Windows on a mac or Install a MacOs in a PC?
If you want to install a Windows on a mac and have windows and mac in the same computer, first you need an Intel Core Processor to use it.
In Mac there are 2 ways:
Paralells Destokp: it install like another mac program, but you can install a windows system into paralells...
Wrong: The only thing i see is the memory.. becouse Mac use a part of memory when start and use it... and paralells use too, then you need more memory tou use.
Good: You can drop documents form mac to paralells from one window to another.
BootCamp: I like it too much and i use it. You can use windows or mac system, but you need to restart your computer to use win or if you are in windows to use mac.
You need 2 hard disk or a partition of 1 and Windows must have Service Pack 2.
Wrong: Need to restart computer. Can't drop files from a hard disk to another.
Good: It's like have 2 computers on 1, the memory and resources is for the operating system you're using in this moment.
In Pc there are a program wich could install a MacOS system but i don't remember it at this moment... i rememeber that i tried it and don't run... i prefer to use into a mac whith core duo BootCamp
If i find which program is for pc and you need it i told you.