When I enter my Sims 3 product code it says ''This code has already been used''.

The same thing happened to me before, and is happening again because my game keeps crashing and not turning back on again. When i tried to reinstall it it said that the product code was already used. The last time it happened i had to buy a new game. But it's such a waste of money, i have two base games now already. It's ridiculous to think i may have to buy another, just for the code.