Free Windows 8.1 iso upgrade

I am sorry if this issue had been beat to death, I am somewhat thick headed, there have been numerous posts on this issue, and it has gotten very confusing , but I wanted to get an ISO of the Free windows 8.1 Pro upgrade, I think I should have downloaded the iso when I first upgraded, however I would still like to have the 8.1 iso on hand. I have a windows 8 Pro, OEM Key. Thanks

Welcome to EightForums

If you have the Windows 8 upgrade, you have a Retail key, not a OEM key.

http://www.eightforums.com/tutorials/18309-windows-8-windows-8-1-iso-download-create.html

This will only work with a Retail key.
http://www.eightforums.com/installation-setup/33164-how-download-windows-8-1-iso.html

You are correct, I downloaded the Windows 8 upgrade from Microsoft at the special price.