Here's a quick tip for you: if after the Spring 2.5 update, you're still seeing problems with the Zune software not reading your music collection correctly, download and run this Zune Media Collection Reset Tool
. It's a really simple tool that, when run, resets the Zune software database - and what that means is that when you next start up the software, it will re-index all of your music, photos, videos, and podcasts from scratch. This can take minutes to hours depending on how much media you have and where it's stored. I was having trouble with some of my music not being recognized properly, and after updating to 2.5, the problem didn't go away. Playing a hunch I ran the reset tool, and as far as I can tell at the moment, all my music is now being read correctly.