Xilisoft Video Converter, not only is it one hell of a video converter, it should also be able to save just the audio of the file, you can even set the start time, and duration of recording, for if you want a specific part.
I've never used it for audio myself ( i use creative wavestudio or mediasource player for audio stuff, but that came with my audio card), but it gets the job done for video, should work fine with audio too.