How to Dualboot or Multiboot or Install 2 or many os in a computer

Requirements :
Minimum hard disk space to install all the operating systems
Minimum RAM to use higher version of windows

Proccess:
It's very easy to install many operating systems in one computer.
Installing the operating systems must be serially from earlier to newest.
Ex- If I want to install Windows XP and Windows 8.1 then I will install winxp first then win8.

AiKON'S Style

Phasellus facilisis convallis metus, ut imperdiet augue auctor nec. Duis at velit id augue lobortis porta. Sed varius, enim accumsan aliquam tincidunt, tortor urna vulputate quam, eget finibus urna est in augue.