If you have a valid Windows 8 product key from a giveaway, online purchase or other source but need the official media this article is for you. Don't risk downloading the ISO file from a torrent, there is a chance you will be installing a copy of Windows 8 infested with malware. Instead, Microsoft offers a free download that is much safer.
Simply download the Windows 8 Setup utility from Microsoft by clicking this link.
Then run the Windows8-Setup.exe file and enter your product key when prompted.
Your product key will be validated and edition automatically determined.
The download will begin and then the files will be prepared. Then Select Install by creating media.
Finally you will be able to select USB flash drive or ISO file.