DirectX version 6.1 is the highest version available for NT 4, and because of this, you may experience some playback problems in Sonicfire. Notably, the effect of only hearing your video's audio and not the Timeline's. On Windows systems using a version of DirectX below 8.0, there's only one 'audio out' for Media Player to use. If you mute the video's sound, you should then hear the Timeline. This effect occurs when playing a movie not supported by Quicktime. To hear both the Timeline and the video's audio simultaneously, the video must be in a Quicktime supported format.