Unless you did a written contract, you are going to have a hard time obtaining a refund. If you took your case to small claims court, it would be your word against their word, and it would cost you money to file. Unless agreed to specifically by both buy and seller specifically, a purchase/sale of an article of property such as a computer is as-is. It would take a much greater misrepresentation such as it was working and didnt, etc., to give you a good chance of winning in court. If you do decide to sue, small claims court is where you go.