If you need to install or re-install Windows 8.1, just download the installation media. Microsoft can allow you to download that image without even entering your product key. Simply download the Windows Installation Media Creation Tool, and then select the details about which version you want and then follow through the wizard to create your boot media. Downloading media can also be useful if you cannot install Windows 8.1 from Windows Store for whatever reason.
1. Downloaded the program from the official website and started it, It allows you to select your desired language, Windows 8.1 edition and system architecture (32-bit or 64-bit).
2. The Next screen shows, whether you want to create a bootable USB flash drive of Windows 8.1 or want to save the setup ISO file of Windows 8.1.
3. The next option display the download progress.