RE: ipod downloading
When you setup iTunes with your iPod you had to establish an authorization between the two. That means you can't have a friend come over with their iPod and copy all your purchased music. All iTunes does is reformat the files structure and renames them to 4 character code names. It then creates a relational database so that only iTunes knows which information goes with each MP3. Most other systems will not be able to decode the reorganization. The files are still MP3s but the data information is reorganized.
To anyone planning on getting an iPod, MAKE A COPY OF YOUR COMPLETE FILE LIBRARY BEFORE MIGRATING IT TO YOUR iTUNES!!! you won't be able to do it later without jumping through major hoops. There are rogue apps out there that can do it for you, though.