On 03 Jan 2017, Red Rum wrote in
alt.comp.os.windows-8:

See
http://www.wikihow.com/Download-Wind...indows_8.1_sub

That did it! I don't think I could have figured that out by myself.
The offer to "add features" without saying what those "features"
are wouldn't have been enough to tell me. But I did have a key
(gleaned by the Nirsoft ProduKey utility) from the registry files
on the old, corrupt disk. Your process accepted that key and went
on to download and install the Media Center components. I have no
way to test it, but it looks like I expected it to. Thanks!

Interestingly, Windows now shows as "Windows 8.1 Pro with Media
Center". Before the added Features, it showed as "Windows 8.1 with
Media Center" - no Home or Pro designation, and no sign of Media Center.

QUOTE:

Windows 8.1

1 Understand the process. Windows Media Center was not
included in Windows 8 when it was released, and is only
available in the Pro version of Windows 8.1. It is not
included in the standard version of 8.1, which means you'll
need to upgrade to Pro in order to use Windows Media Center.
This is the only legal way to get Windows Media Center on
Windows 8.1

[...etc., etc...]

5 Add the new pack key to Windows 8.1. Once you have the key,
you can enter it in Windows so that your upgrade can be
downloaded and installed.
* Press Win and type "add features".
* Select "Add features to Windows 8.1".
* Choose "I already have a product key".
* Enter the key into the field.