Thanks in advance for reading and considering... I switched from Windows to Mac a couple weeks ago, and transferred a sizeable gallery of mp3s, close to 100G, most of which I got from ripping from CD, or from emusic, or from the Russians, back when it wasn't so hard to do that. (I also had a sizable collection of subscription tracks from Rhapsody, but we won't go there, not now.) My personal music players have always been from Creative Labs; call it a personal preference. However, my daughter has always used iTunes; I've had an iTunes account for about 4 years, and I had her set up on an allowance for a while, until she got older and decided she's rather have cash. When I transferred my library of mp3s to my MacBook Pro, everything transferred over as mp3s. Yesterday, when I was browsing my library, I noticed duplicates and sometimes triplicates, all through the list! Checking the file location, I found that a large number of my mp3s are now on my computer not just as mp3s, but also as m4ps AND m4as! The problem with this is manifold. First, disc space. I don't need 250G of triplicates; 80G of single copies is plenty. Second, it's just wasteful; there's no benefit to having the same track in multiple format that I can see (especially if one of those formats is DRM protected). Third, I really like the Genius playlist feature; but if the Genius chooses a version of the track that is m4a or m4p, then the playlist can only be burned to CD either a) without those tracks (easiest way), or by deleting those tracks from the playlist and inserting the mp3 version in their place (a PITA for a 100 track playlist). Where did all these m4a and m4p tracks come from? I didn't buy them. Did The iTunes Store automatically download them to my computer because my daughter had purchased them on my account? Does the iTunes program have a setting I couldn't find that automatically converts mp3s to m4as and m4ps? I'm at a loss.