Why are my Itunes folders empty on Tivo?

I am sorry to bring this up again, but I am still having problems that my Itunes folders appear empty when I try to play them through my TivoHD. I have read about conversion programs, but from what I understand these are already MP3 files? I guess I do not understand enough about the file formats that Itunes uses on my PC or the sharing rights. Is this something that I can fix. My goal would be to play music MP3 and podcast MP3 through Tivo without a big hassle.

My specs:

PC running Windows XP Home Media version 5.1 SP2
Itunes version 7.3.2.6
Tivo Desktop version 2.5.275381
Tivo HD version 8.1.7b2.01-2-652
Wireless G Tivo adapter

Thanks for the advice

Mike