As some of you might have noticed, Windows Media Center is disabled by default in Windows 8 Release Preview. Here’s how to re-enable it according to the Microsoft FAQ:
f you’re running a 32-bit version of Windows XP, Vista, or 7, and you wish to upgrade to the 64-bit version of Windows 8, can you do this via Upgrade Advisor? Will that work? (Or vice versa, though I can’t imagine anyone wanting to go from 64-bit to 32-bit.)