It seems that my Double Deluxe game will only allow me to have the University and Business expansions. Yet, I keep hearing that it is possible to add others. I want to add Pets and Seasons. Installing these is easy, but once installed, the game will not open. It tells me to use the Seasons disc, so I do. Then I try to open it, and it tells me to use the Double Deluxe disc, so I try that. It tells me to use the Seasons disc again! How do I make these games work together?