You need to purchase the Windows Media Center pack separately in order to add DVD playback back into your OS. It will be available to Windows 8 Pro users on October 26th.
According to the Building Windows 8 Blog, by default, Windows 8 does not come with DVD codecs. This is because codec licensing costs are non-trivial, and many computers no longer come with a DVD drive in the first place.
If you're currently using Windows XP, Vista, or 7, you can upgrade to the full Windows 8 Pro With Media Pack for $40. If you already have Windows 8 standard installed, you will be able to purchase a Windows 8 Pro upgrade pack through the Microsoft Store (currently available for pre-order), which will enable you to install Media Center.
Media pack is not pre-installed with Windows 8 Pro. There is no official word yet on what it will cost to add the Media Pack to Windows 8 Pro separately, but it will be available as an optional add-on.
As per this official blog post though, Windows Media Center can be added for free through the Add Features option within Windows 8 Pro after the $40 upgrade, at least till January 31, 2013 (that's the last date as of now for the low upgrade price, though Microsoft may choose to extend the date of course). Further, if the Windows 8 Pro System Builder version is installed, Windows Media Center can be added to it as well via the Add Features option for free during the promotion.
Of course, you can always purchase 3rd party DVD playback software, or use something like VLC or any other free player+codec pack combo that provides this feature.
I thing you have to install a special package to play DVDs with digital restrictive rights. – ctrl-alt-delor – 2012-09-19T09:04:07.710
Are you expecting it to play just by inserting it. Maybe Microsoft have disabled this annoying, and sometimes dangerous behaviour. Try the play button, in one of the movie players. – ctrl-alt-delor – 2012-09-19T09:05:21.080
No I don't. But I also noticed lack of this function. – Piotr Krysiak – 2012-09-19T09:05:55.713
I just noticed a footnote that mentions this.
– Synetech – 2012-10-26T18:56:26.087