Trying to resurrect my brothers ancient gateway

I figured out beside the product key on the Gateway that the OS is 'Windows XP Media Center Edition 2005'. It's my brother computer and I don't remember seeing a disc for that version of windows. I'm trying to repair it with Windows XP Pro SP2 which is from my other PC, which code should it be asking for then?

Shouldn't the code work for the disc I'm repairing it with? I'm just confused as to which code it's even asking me for