Windows Media Player 11 will normally be unable to play a high-definition movie such as an MP4 H.264. To fix this problem, you can download a codec pack designed for the native program Windows Media Player that will expand the video capabilities of your player. Windows Media Player 11 will then be able to play a wide variety of video formats that it cannot handle on its own.
Download and install a codec pack for Windows Media Player such as Media Player Codec Pack (see Resources). This add-on software codec is completely free and will run passively in the background after installation.
Right-click on your MP4 H.264 video file.
Select "Open with." A new set of options appears. Select "Windows Media Player." The program will open and begin playing your file.