This is not anything you can fix. Hard drive and Flash Memory manufactureres measure 1GB as 1000 MB. Mac OS and Windows (and therefore their programs) measure 1GB as 1024MB. This means that what you see in your iPod's About section and in iTunes is less than the 4GB you were expecting. Apple also does not directly test their products. They measure 1 song as 4 minutes, encoded in AAC format with 128-bit encoding. I quote directly from the Nano page under the iPod + iTunes tab viewable in EVERY apple page "Song capacity based on 4 minutes per song and 128-Kbps AAC encoding; actual capacity varies by content. 1GB = 1 billion bytes; actual formatted capacity less." For everyone out there, that means that Apple's famed AAC format, encoded at 128-Kbps (kilobits per second), which is the highest quality, and 4 minutes a song, you can store ABOUT 1000 songs in 4GB. Once the iPod is formatted, it takes on the file system that sees 1GB as 1024MB. That means you can't store as many songs, and if the song is longer than 4minutes, it will be larger and that means it takes up more space. The ID3 tags (what you see when you look at your iPod's screen that shows Name, Artist, and Album while playing a song) also take up a bit of space in the song data. Album Artwork also takes up space and is encoded into the song as well. Ratings, comments, lyrics, ID3 Tags, and Artwork all take up extra space, further limiting the songs you can take with.
