Q: How do you put the iPod Nano into Disk Mode?
A: 1. Press and hold the Menu and Center buttons for about 10 seconds until the Apple logo appears.
2. Continue to hold down the Center button, but take your other finger off of Menu and start holding down the Play/Pause button right as the Apple logo appears. (Center+Play/Pause)
3. A screen will appear that says OK to disconnect with a check mark. This will mean you are in Disk Mode. You can now connect the device to your computer.
To exit Disk Mode, reset your iPod Nano.