Easiest way to convert ANY format for which you can't do a direct conversion, is to open Audacity (or another Wave editor) and have it record whatever is being sent to the soundcard. So bring up RealPlayer, play the song, and then hit record on Audacity. You'll then have a wave file you can convert to MP3. BUT - Audacity will record ANY sound your PC feels like playing, so if your Outlook decides to get mail and you have it setup to play some cute sound alerting you of the new mail, this will get recorded by Audacity, so shutdown anything that might "speak up" during the recording.
I had to do this to get the David Gilmour Concert DVD into mp3 form (for my own use!). It worked really well, but it took awhile to chop up the concert into individual tracks. I think the DVD was "rip" protected or something. (please forgive me Mr. Gilmour!)