Step 1: Download the Windows 7 USB / DVD Download Tool from here.
How to use Windows 7 USB / DVD Download Tool to create Windows 8.1 bootable USB / DVD: To create a UEFI compliant bootable USB, you need to use Rufus, the best free tool available for the job. That is, you cannot use this tool to create a bootable USB to install Windows 8.1 on a UEFI computer. The other downside to this tool is that it doesn't help you create a bootable USB for UEFI computers. While the Windows 7 USB / DVD download tool is certainly not the best tool in its class, and free tools like Rufus easily outperform this official tool, users who aren't comfortable with third-party tools prefer to use this tool.