If they're older songs you bought on iTunes, they're likely locked down with DRM, meaning you can only play them on machines authorized with your iTunes account credentials.
If new music plays but old music doesn't, you might have logged in under a different user name/password when you bought the new music?
Check how you're logged in, and make sure you use the Authorize command in the iTunes menu to make sure the machine you're trying to play the music on is authorized.
01-16-2009 04:07 PM