Hoy,
You buyed it from E-bay,did i get that right?
It might be possible that you are nailed.Prohably the former owner installed the game on his computer with the licencekey-code.
Than he sold the disk without the keycode to you,this way he get atleast some part of his money back.
Why dont you all buy the game in registrated stores,or even by download by the company itself.This way you are sure that it is a legal copy,and with the keycode togerther in the box.
If you dont have your keycode,maybe send a message to Mad_Fred.However by the story you told i doubt it if he can help.
By the way,howmuch did you pay for the game??