I think the best way to organise your MP3's is manually.
If you go onto the removable drive, double click on the MP3 folder.
In this folder, create a folder for an artist, then a subfolder for the album name, and then put your MP3 tracks in that.
I found that I wouldn't be using full albums so I've made folders along these lines:
../MP3/Various Artists/Pop/
../MP3/Various Artists/Rock/
../MP3/Various Artists/Soundtracks/
or even
../MP3/John Lennon/Various Tracks/
With these folders, you should have 'Various Artists' and 'John Lennon' listed under the walkmans Artists list. You should have 'Pop', 'Rock', 'Soundtracks' and 'Various Tracks' under the Albums list.
Hope it helps!