If you go to the store, you may find two packages: Windows 8 Pro and Windows 8 Pro Pack. They look similar, and currently priced the same. So what's the difference?
Windows 8 Pro is for customers who already have WinXP/Vista/7 to upgrade to Win8 Pro. By default, it does not come with Media Center; however, for a limited time you can add Media Center to Windows 8 Pro for free directly from Microsoft's site. (By extension, Windows 8 - regular or Pro - will not be able to play DVDs by default, unless you install Media Center or 3rd party DVD player software.)
Windows 8 Pro Pack is for customers who bought new PCs that comes with (standard) Windows 8, and want to upgrade to Windows 8 Pro with Media Center functionality.
What if you say "I don't need all the features in Windows 8 Pro. Can I just get Media Center for my (regular) Windows 8?" You can't - you cannot get Media Center on top of (regular) Windows 8 without upgrading to Windows 8 Pro.
