My iPod Classic shows link to support

Hello, I have an iPod Classic 20G. When I turn it on, the apple appears and stays for a few seconds, then it displays an iPod on screen with the link to Apple.com/support/ipod. When I go there, I try to get help with a tech. It asks for my type of iPod and the serial number, but when I enter the information, it says the serial number is not valid. What can I do in order to get my iPod Classic to work again?