Vista - Speech Recognition with Audio File

I am using Window's Vista and am trying to use speech recognition. I have an
audio file of an interview (only one person talking, and quite clearly) but I
want to use Speech Recognition to turn it into a Word or Wordpad document.
Does anyone know the right way to do this?

When I speak into the microphone, it picks up all of my words clearly, but
when I play the audio file into the microphone, the computer doesn't
recognize a single word, even though I have it loud and clear. It starts
putting down bizarre words (like ones about baseball). I have been playing
the audio file on my laptop's speakers and trying to play it into my desktop
computer's microphone. Is there a proper way to do this?