Here's Apple's article on backup and restore.
http://support.apple.com/kb/HT1751
I see a lot of folk ask how to restore but first we have to read about their backups.
Bob
I am in a band and we frequently purchase karaoke tracks. Going on in our usual way of doing thing we look at potential songs we have then decide to purchase new ones. The store was working fine, we logged in to buy a track and it says the internet connection is not available. We try a different song, same result. Then we close iTunes to reboot it. Once this happens all of our many playlists are gone. Many tracks are missing, and we get the same errors. We find iTunes library extras and the genius program in the recycle bin. Tired to get help through iTunes but all their websites don't work eithhave restarted system I cant fix the error I made so ignore it. Basically we did everything to try and restore files and they still dont show up in iTunes. Any and all help is appriciated.

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