1. VLC Media Player (highly recommended)
2. Free version of RealPlayer
As probably the world’s most widely used media player, RealPlayer allows media playback for almost any formats. It plays more file formats than Windows Media Player as announced on its official website homepage.(FYI)
There are many other free options to play DVD in Windows 8 PC, such as SMPlayer (with MPlayer as its playback engine and its own codecs without codec packs installment which save you much trouble), etc.
In spite of the media player as options for DVD playback in Windows 8, you can probably try other methods as well. DVD rippers to get the DVD videos in other formats for playback would be another way, I suppose. After all, it seems that Microsoft tried to strip the DVD playback function for consumers’ sake of reducing fees as has done of the opposite, I’m afraid.