Re: iTunes backup problem
Sometimes iTunes decides to rip/download music to other folders. Maybe the missing files are on another drive/folder somewhere?
I had exactly this issue with my wife's PC. She purchases music on iTunes store as well as ripping her own CDs. Sometimes, iTunes will forget that I told it where to put the downloaded stuff, or where to rip CDs to, and I have to reset it.
I think you'll find that your missing tunes are there, just in another (possibly iTunes default) folder.
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