Watch this is you want to move all of your iTunes from one computer to another, even if it's across platforms (eg. PC to Mac). This uses iTunes 9 Home Sharing.
I hope this helps you out, as I did a fair bit of research and this seems like the most straight forward way to move all of your music, movies and podcasts etc from one computer to another, and I didn't find this solution anywhere. It just seemed like a logical way to do it.