GOM Player is a freeware player for DVDs and Video Files that offers advanced features and a really slick look-and-feel. Most importantly, it comes with its own resident codecs, meaning that you WILL be able to play pretty much every format without needing to find, download, and install different codecs for different formats. It also purports to have patented technology that allows you to play partially downloaded files! I haven’t tried this, but it sounds good to me.
A free alternative to: PowerDVD, WinDVD
Version tested: 2,0,9,360