how to download and activate clean installation of window operating systems

visit
http://getintopc.com/softwares/operating-systems/
select the official OS you want to download.
then click set up on the iso you download, if product key is required visit http://www.eightforums.com/tutorials/2299-clean-install-windows-8-a.html
for suitable product key. you don't have any problem. TESTED, IT WORK FOR ME...