A friend of mine started using CCleaner and had Last Download Location ticked. According to him this completely wiped out his itunes collection, as that was where he last downloaded to before using CCleaner. He only realised what had happened days later when trying to access his files and they wern't there, and began a working backwards in time diagnosis. As he lives in another country i can't actually verify this was the cause, and i don't have itunes, but i thought i'd offer it up as a talking point to see what you think. If it's correct, then this could be a big problem for all sorts of things with that option ticked.