How did you install realplayer 10, exactly?
Why did you install such an outdated OS when uptodate versions are available much more easily?
If you just want to play mp3s - there is an mp3 plugin for xmms.
Look at mplayer - I think the RH9 notes are still up at www.mjmwired.net
- mjm's mplayer setup includes definitive instructions for getting realplayer going too - with the bonus of playing and editing video formats as well
But really: just convert the mp3 files to ogg/vorbis format, then play them.