Hmm, I've realized that you are talking about a music file....., before I thought it was a video file.
Maybe the Super converter ain't that good at converting music files, so it supports that function. But then you have to use MP3 as output format...
In case it won't do it either with the changed output format, you could try this free audio converter.....though I haven't tested this one yet:
SC Free Audio Converter 7.0.0.0 