To hard-reset a seventh generation iPod Nano, press and hold the Sleep and the Home buttons until the screen goes dark. Release the buttons after seeing the Apple logo, followed by the Home screen. For a sixth generation iPod Nano, press and hold the Sleep and the Volume Down buttons for at least eight seconds. Release the buttons when the Apple logo displays.
If these steps don't work, connect the iPod to an electrical outlet or to a computer to charge for a while, and then repeat the steps. Do not attempt to reset the iPod while it's connected to a computer. To reset an iPod Shuffle, first move the power switch to the Off position. You shouldn't see the green stripe after this. Wait for at least ten seconds, and move the switch to one of the play positions.
If your iPod features a click wheel, slide the Hold switch to the locked position, and slide it to the unlocked position. Next, press and hold the Menu and Center buttons together for approximately eight seconds. Release the buttons when you see the Apple logo. If this doesn't work, repeat the steps ensuring you aren't touching the click wheel as you press the Center button. Additionally, press the Menu button near the outside of the click wheel, not near the center.