VLC media player is a highly portable multimedia player for various audio and video formats (MPEG-1, MPEG-2, MPEG-4, DivX, mp3, ogg, …) as well as DVDs, VCDs, and various streaming protocols.
It can also be used as a server to stream in unicast or multicast in IPv4 or IPv6 on a high-bandwidth network.
It doesn’t need any external codec or program to work.

Every Video or DVD Movie I have thrown at VLC, it has been able to play. It’s free of spyware/viruses.