So, this happened only recently, but all of a sudden, I can't play any of my video files that I was able to play in wmp just a few days ago. All of a sudden, whenever I try to open a video file, i just get an error that says: INTERFACE NOT REGISTERED. When I place these files into windows live movie maker, they play fine and i can even edit them. As for windows media player, the only video I can play is the sample HD video with the animals. Would appreciate if anybody could help me with this problem and has a solution for this 'interface not registered' video error. Thank you s omuch.