It says at the back of the box it requires the sims 2, the sims 2 special dvd edition, the holiday edition or the deluxe. You can choose either one. The main idea is you have to have the sims 2 base game to install any expansion pack. Like i said, you can choose either the deluxe or the holiday because each one includes the sims 2 base game. If you already have the sims 2 installed, there's no need for the deluxe or the holiday to install the seasons expansion pack. I'm really hoping you can have the seasons installed because for me it is the best EP there is.