There is no way to convert from AAC to any other widely used format becasue it's so obscure and Apple is the only one that uses it. Besides, they've put some sort of lock on that format so no one can duplicate their software (which I think is so selfish). You'll have to find .wav, mp3, Real, WMP, etc version of it to play on your xanga. Check the
Big Book of Resources for a long list of music sites.