"A friend downloaded some television programmes for me. When I try to play them with Windows Media Player I only get the sound and no pics. What do I need to do to watch these programmes?"
Video files that play the sound but don't play the video are more common than you might realize. This problem is almost always caused by one of two problems. Either you don't have the required codec installed on your system to decode the video portion of the file you downloaded or Windows Media Player isn't properly associating the correct codec on your system in a way that makes viewing video possible. This is complicated by a huge volume of codecs out there. Here's how to get the file to play:
Finding the right codec
The first step in correcting playback problems is finding the required codec(s). Most files require one codec to display the video and a different codec for displaying audio. My favorite tool for locating codecs is MediaInfo, which is a free download.
MediaInfo locates many video playback issues by identifying things like the length of the movie, which it compares against the expected length embedded in the file to determine if you have a complete file. MediaInfo tells you which codec is required for video and audio and how many of the codecs on your system are capable of playing back a file. A preview feature simulates file playback to determine if the software can render the file correctly.
If MediaInfo determines you are missing a codec, you need to locate that codec online and download it. In most cases, there's a link to the correct codec right inside MediaInfo.