1. Connect your iPod to your computer and open iTunes.
2. Select iPod in the iTunes source list.
3. Click the iPod options button in the lower-right corner of the iTunes window.
4. Click the “Enable disk use” checkbox, and then click OK.
5. Close iTunes and notice that your iPod appears on your Mac desktop or in the Windows Explorer on your PC.
6. To eject the iPod on a Mac, select the iPod on the desktop and drag it to the Trash.
7. To eject the iPod on a PC, select the iPod in the Windows Explorer, right click on the iPod and then choose Eject from the pop-up menu that appears. Or at the bottom-right of the screen, click the ‘Safely Remove Hardware’ icon.
http://www.apple.com/support/ipod/tutorial/ip_gettingstarted_t13.html