Windows Media Center has been taken out of Windows 8, but is available as a pay-for added extra. But if you are quick, and you want Windows Media Center, you can get it for free.
Several features present in Windows 7 Professional are no longer there in Windows 8 Pro. Furthermore, the upgrade process gives you no warning that these features will be removed. Most of the features can be put back if you wish, thanks to some third-party applications.
One exception is Windows Media Center which has been taken out of the core Windows distribution and made available as an extra you'll have to pay for. However, Microsoft has made the add-on free for Windows 8 Pro users until January 31st 2013.
Go to http://windows.microsoft.com/en-US/windows-8/feature-packs and supply your email address, and Microsoft will send you a product key to enable the feature free of charge. If you're too late, you'll have to pay. (See also: Windows 8: the complete guide.)