http://www.dbpoweramp.com/ check the link out and yes it is free. Just make sure you get the codecs they offer to convert multiple formats
I just wanted to throw this in. Although the audio player turned out to be a little "buggy" (could have been my PC), [bold]the music converter is a very nice app. The file tagger function is one of the best that you will find.[/bold] I was so impressed with the music converter that even though I don't encode in mp3, I went back and purchsed the converter "Power Pack" for a quite decent $14. The Power Pack allows you to have faster ripping speeds and also some pretty good DSP features.