Windows 8 no longer ships with the copyrighted/licensed software to play commercial movie DVDs. Microsoft got tired of paying royalties on every copy of Windows it sells. However, the free, open-source software VLC Media Player, being developed from France, ignores DVD copyright issues and will play them for you for free. It also plays pretty much ANY type of video or audio file made:http://www.videolan.org/vlc/index.html
Just hit the big orange Download button!