Currently Being ModeratedNov 24, 2012 7:22 AM (in response to joshuaracecar)
Head to this page: https://supportprofile.apple.com/MySupportProfile.do
Click the appropriate product and there should be an unregister button.
You'll also want to restore the iPod Shuffle to factory settings in iTunes. This process wipes all content from the iPod, resets all settings back to their defaults, and reloads a fresh copy of the iPod's software onto the device.