[REQUEST] Halo 2 activation key(s)?

Hey all,
I just bought Halo 2 a few days ago from Kroger, but every time I try to activate it, it says the key has already been used.
I looked up keys on the internet, and all the ones I found (Including the ones here), haven't worked.
If anyone has one, may I please use it? If so, please PM me.