The info for playing sounds is incomplete, while using WMP engine to play normal .MP3 files stored home: relatively is not currently possible, that is not the only way to get a MP3 encoded file. SndRec32 (Start | Programs | Accessories | Multimedia | Sound Recorder) that comes with win95 and above can convert standard PCM .WAV files to MP3 encoded at up to 56Kbps stereo .WAV files that worlds can play quite happily. Simply load the PCM .WAV file into SndRec32 and select File | Properties.
Then select in format conversion box "Playback Formats" and hit convert now, select Format: to "MPEG Layer-3" then select a bitrate and mono/stereo mode appropriate to the file you are converting and hit OK button. Save that and you will have a .WAV file containing MP3 encoded data and worldsplayer can play it quite happily. Only issue is MP3 does not necessarily start and end at a zero or neutral sample value so looped samples may click as they end and restart when straight PCM .WAV would not.