Here is how I got around this problem: http://lukesdyer.info/techie-tricks/how-to-downgrade-from-windows-8-professional-media-center-to-windows-8-professional/
I own a copy of Windows 8 Pro which I bought from Newegg, and I did a clean install on my new computer. I activated Windows, and everything was running perfectly.
I needed to play a dvd, so I requested a key for Windows Media Center, which comes free with the pro version of windows 8. When the key came, I followed their instructions: Search -> Add Features to Windows 8 -> Enter the product key -> Install. The install worked fine, and it restarted.
When it came back up, there was a watermark at the bottom right of my desktop saying, "Windows 8 Pro with Media Center \n Build 9200." Even more annoying, however, is that my copy of Windows 8 suddenly needed to be activated again. When I tried to do so, I got the error code: 0xC004C4AA. I looked this error up, and it turns out that Windows Media Player isn't allowed on my copy because I didn't get it directly from Microsoft.
(Also, I am no longer able to "Add Features to Windows 8" anymore, not that I would be inclined to do that ever again after this.)
This has just been a complete hassle, so my question is, How can I undo adding WMC to my computer, so that it will just go back to how it was?