When you install iTunes for Windows, it defaults to the setting that automatically keeps your iPod in sync with your iTunes library. That means if your computer doesn’t have much music on it, and you plug in an iPod that you’d topped off with music from another computer, all the music on your iPod will get wiped out. Worse, there’s no way to change this behavior without first plugging in an iPod. Catch-22. Stupid, stupid product design.