wrong length of the movie in windows media player 11

Whenever I exclude commercials while converting from HD to mpeg, the Win media player determines the length of the resulting video incorrectly, e.g. it takes the length of the first fragment before the commercial as the total length of the video.


For example, if the commercial first appears at the 15-th minute then WMP will assume the total lenght of the video is just 15 minutes, even though it would be able to play the whole video past the 15 minute mark. But you are unable to start the playback from any point after the first 15 minutes.

Could you help me?