[Anomalous]

Does anyone know a way to load Windows Media audio files onto a Rio 600? The player supports that format, but you can't load WMAs with iTunes. Under Virtual PC, Windows Media Player doesn't recognize the Rio 600 no matter what I do. Thanks.

[SupahCoolX]

Since WMA is a Microsoft "standard," there isn't too much out there that actually works with it besides Windows Media Player on the PC. Try, perhaps, MusicMatch Jukebox or Audion. If either of those supports WMA, then they might be able to do the trick.
Otherwise, you could always rip those songs again as 64k MP3s. Their size will be about the same as WMA, and the quality should be comparable (though I'm no acoustic expert).

[Anomalous]

Thanks. I tried RealJukebox under Virtual PC and that didn't work either, but I did already have a copy that I reripped as an MP3.

[GORDYmac]

If you're the owner to the file you're trying to put on the Rio, then just download the MP3 verion, if possible (http://www.xlife.org/acquisition.php).