Upgrading Windows 8.1 edition to Pro

The problem
I’ve recently got a new laptop with licensed version of Windows 8.1, however I needed a Pro version since I need Hyper-V. So… I downloaded “multiple edition” setup ISO from MSDN and repaved the machine. It did not ask for a product key and just got activated automatically as a standard edition. After searching around I found out you can change your product key (in a couple of ways) so I gave it a shot with my Pro key. But I was greeted with an error message.

That key can’t be used to activate this edition of Windows.

Googling and Binging around didn’t help as everyone pointed to using an “Upgrade key” which is a different thing. This doesn’t work for me since I’m MSDN subscriber. Why in hell would I then buy another key? I won’t budge… Go for another longer session of search…

The solution

Disable User Account Control

After disabling UAC changing product key worked like a charm. I’m amazed as anyone else…