If you were running Windows 8 Pro with Windows Media Center and you download the Windows 8.1 preview through the Windows Store, Windows Media Center will be retained and you don’t have to reinstall it. But if you have installed Windows 8.1 preview using the ISO file, Windows Media Center will be removed. So you have to reinstall it with your original Windows 8 Pro pack or Windows 8 Media Center Pack product key.
Let us see how to reinstall Windows Media Center if you are having the media center Product key.
Open Control Panel > System or you can press WinKey+Pause/Break to open System.
And click on ‘ Get more features with a new edition of Windows’
Click on I already have a product Key and enter the Media Center Pack product key when asked. It’ll check the key and will install the required feature. During the process PC will restart at least once.
After the restart if you check the Control Panel >System , your Windows edition will now be shown with Media Center
And after adding Windows Media Center your DVD playback feature too will be activated in WMP 12 , if you aren’t running any 3rd party media player.