How to Migrate form Operating System

Hi,
I have bought a new computer where it was shipped with Windows 7 and I am not so comfortable with that. So I am looking for shifting to Windows XP before I dump my huge files onto my computer, where doing it in the later point may make it more tough, where I need to take back ups.
So please guide me to install Windows XP. I can even Google it but I just wanted to rely on expert comments, to make sure my brand new computer stays safe.
