New answers tagged windows-media-center
You should be able to just do an in-place upgrade to Windows 8.1 Pro... From MS: Windows 8 and Windows 8.1 Upgrade Paths You can upgrade to Windows 8.1 Pro and keep Windows settings, personal files, and applications from the following Windows operating system editions: Windows 8 Windows 8 Pro Windows 8 Pro with Media Center Windows ...
You have to go through the OS to buy a Media Center key. And, to complicate matters further for what you want to do, Media Center is an add-on, not a separate installation - so you need to reinstall Windows 8.1 Pro regardless... Sorry for the bad news!
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