If you added the Windows Media Center feature pack, and then tried to use your new product key, you might have found yourself with some ridiclous message in the lower right hand corner of your screen. Specifically:
Windows 8 Pro with Media Center Build 9200
Getting rid of it is pretty easy, though it shouldn’t have been this way. After adding your pack product key, you’ll restart a couple times and you’ll get back into Windows. Then, you’ll need to re-activate Windows which is effortless. Just search for Activate under Settings on the start screen. Then you can either crash Explorer, Desktop Window Manager or restart, and if you’re lucky, the watermark message will be gone from your screen.