I use the DefilerPak and Media Player Classic. (Both approved by Something Awful) I also have Real Alternative (as opposed to the bloatware) which came with an installer for MPC. I've been able to play just about any codec I throw at it. It can take any container (avi, ogm, mkv), audio codec (mp3, AAC, ogg), and video codec (DivX, Xvid, MPEG4, H.264).