play home network whit mirror ?

[poupout]

hi, i have a problemi want to play a game on home network on the first system i have the original cd of the game and on the second i play whit mirror of the original cd but wen i try to play it tell me the serial number is used. so my question is what can i do to play that game? can i change the serial of the mirror? or else give me your suggestion.
thanks