Sims 3 Pre-owned copy won't install

I recently bought a pre-owned copy of Sims 3, and I can't install it because the product key has already been used. I was wondering if there was any way around this, as I really can't afford to buy yet another copy of the game.

I don't care about all the online stuff, and would just like to play the game (which I assumed I'd be able to do by just having the disc, but Origin won't let me install without a valid product key).

This is the first time I've purchased The Sims for my Laptop, and am a little let down, I never had all this hassle when I bought the games for my PlayStation.

Thank you.