It’s as if Microsoft is going out of their way to prevent us from using Windows Media Center in Windows 8. A user at the Microsoft Answers Forum noticed that there are a couple of things missing from the Startup and Window Behavior options within Windows Media Center in Windows 8. The options for always keeping Windows Media Center on top and starting Media Center when Windows starts have both been removed. A Microsoft employee, going by the name Nico T, responded by updating the FAQ with the following:
Due to new Windows OS requirements and behaviors, these two features have been removed from Media Center in Windows 8.
So,if you were considering upgrading a dedicated home theater PC to Windows 8, Microsoft may have given you one more reason not to do so.