Installation of Windows 8.1 with a Windows 8.0 Product Key Notes

One of the worst mistakes Microsoft made with the Windows 8.1 update was having Windows 8.1 installation media reject Windows 8.0 product keys and vice versa. 
Update 08/11/2014 This is now rectified with the new Windows 8.1 with Update 1 Downloader which allows selection or architecture, Windows 8.1 version and language.

• Download Windows 8.1 Retail and OEM .iso

The updated .iso accepted both the generic Windows 8.0 and generic Windows 8.1 product keys during installation and so should work with all retail licenses.
Full testing is not yet done with the OEM license and the new .isos yet but they are reported to work with some of the workarounds I have previously documented.

Tutorial Video

Player 1: YouTube

Player 2: WordPress

Install Windows 8.1 with a Windows 8.0 Retail or OEM Product Key

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Additional Notes

Installation is still possible with the use of generic product keys.

Identifying whether you have a Windows 8.0 or Windows 8.0 Professional license

If you have purchased a retail license you will be explicitly told on the installation media whether your license is:

• Windows 8.0 → Use the generic Windows 8.1 Core/Home product key 334NH-RXG76-64THK-C7CKG-D3VPT. After installation use the BIOS Embedded SLP Key with “Change Key” as described here.
• Windows 8.1 → Use your Windows 8.1 Core/Home product key. The system will automatically activate when connected to the internet after installation.
• Windows 8.0 Professional → Use the generic Windows 8.1 Professional product key XHQ8N-C3MCJ-RQXB6-WCHYG-C9WKB. After installation use the BIOS Embedded SLP Key with “Change Key” as described here.
• Windows 8.1 Professional → Use your Windows 8.1 Professional product key. The system will automatically activate when connected to the internet after installation.