I bought 2 Windows 8 upgrades, 1 for my PC and 1 for my notebook. I added Windows Media Center to my notebook using the free offer in November (side note: the key was emailed to me within 5 minutes, I see many people have been complaining that it takes a few days).
Today I decided to add WMC to my PC as well, so I went onto the Microsoft website, same like last time, and I received the email within a few minutes. Once I added WMC, entered the key and the computer rebooted, my activation is now broken:
This product key is already being used on another PC. Try a different key or buy a new one.
After rereading the product key email, I realised that the WMC key was exactly the same as the one I had received in November for my notebook (I used the same email, i.e. my Microsoft account Outlook email, for both). I didn't think this would be a problem, as on Microsoft's feature pack page it states:
...is limited to five licenses per customer per promotion.
So then I decided, I'll just remove WMC from my PC and go back to Windows 8 Pro. So I turned off the WMC feature, PC restarted, activation still broken because my key has been replaced. I then tried to activate it with my original Pro key. The error it gave was that this key cannot be used with this version of Windows, as it is now Windows 8 Pro with Media Center and not Windows 8 Pro anymore.
I've searched a bit and it seems the only way to remove it is do a clean install. I tried the Windows 8 Downgrade Helper, which told me I was already running Win 8 Pro when I tried to downgrade, and that I was running Win 8 Pro with Media center when I tried the other option.
To sum up: How do I remove Windows Media Center from Windows 8 Pro without having to do a clean install?