Go buy a PC game at Best Buy. Tell me what the return policy is plz. Last time I tried they told me you can't return PC games, especially if they have already been opened.
So....no I'm not retarded.
Different places have different policies. Target allows trade-ins on open hardware, with occasional exceptions (D3 is one of those exceptions). That is, they'll give you a gift card for whatever amount you paid. I've done this more than once with PC games over the last 12 years. It only recently became the norm for you not to need a CD running to play a game.