Most of the earlier generation of iPods also have the ability to serve as an external hard drive for your computer too, and it’s likely that’s related to the message you are seeing: when first set up, an Apple iPod is either formatted at the drive level to be Mac OS X or Windows compatible. While Apple has released many generations and styles of different iPod units they’re all still basically a hard drive with fancy software to make them seem like sleek, easy to use music and media players.