Obtaining Installation Media for Windows 8.1
The link below offers an utility to create installation media for Windows 8.1. Once downloaded and executed, the application will ask a few questions such as 32-bit vs. 64-bit. The user account in question must be a member of the local Administrators group before the utility will launch correctly.
http://windows.microsoft.com/en-us/windows-8/create-reset-refresh-media