iTunes says it can find the file anymore. What happened?
iTunes is in this aspect a strange program. When adding files to the library to play it later, you are actually only adding references to the original files. If you later delete or move the original files, the music still shows in the library, but the references are no longer valid. You can avoid the frustration over this non-intuitive feature, by going to the advanced settings and check the option saying “Copy files to iTunes music folder when adding files to the iTunes library”. You can read about iTunes and moving files around on this page.
