A while back I had purchased a copy of Windows 8 Pro (more specifically an "Upgrade" copy) for a custom PC build that had Windows 7 installed. Progressing through the usual installation and successfully upgrading to Windows 8 Pro, I was informed that Windows 8 was not officially supported by Microsoft anymore and that I needed to upgrade to Windows 8.1 to continue receiving security updates and such.
After updating Windows 8 to allow me to upgrade through the Windows Store, I got a notification about downloading and installing Windows 8.1 Pro, and without any noticeable problems at first, the upgrade went smoothly. Though, after upgrading, my Intel HD Graphics drivers stopped working and even after reinstalling drivers, fresh from Intel's website, they refused to work. After checking for any system file corruptions (which detected none) in Command Prompt, the driver problem persisted.
So after much troubleshooting, I decided to go the clean installation route.
I had heard extensively among other users that Windows 8.1 could be activated with a Windows 8 product key, after going through the installation using the Windows 8.1 Professional KMS product key freely provided by Microsoft.
Knowing that my Windows 8 product key was definitely genuine, I typed the key into the Product Activation, and Windows immediately gave me an error that the product key inputted was not correct or valid.
Does "Upgrade" product keys activate differently if activated through retail copies of Windows (say from an ISO downloaded through Microsoft)?
Has anyone ever activated Windows 8.1 Pro using a Windows 8 Pro "Upgrade" product key and done successfully?
Useful information would be greatly appreciated. Thanks!