How did you pay? If you payed through your bank(debit card) go talk to your banker with printouts of the advertisement for the sale and "all" documents related to the sale along with the modules. Explain to the banker that you did not receive the exact item you ordered an you want to make a "stop payment" to the seller, if need be, the banks can also contact eachother to note an action as 'hold' until both parties have been contacted. Your bankers will be more than willing to help you and you will get a quicker response from the seller once his/her bank notifies of the issue of funds being stopped in route. My bankers have helped me on issues like this before when buying off the Net, with much faster results than the net.
Believe that when he notices his money not getting to him, he'll want his stuff back, which you will be ready to do!
Always remember your bank card is also a security trust. Your bankers are always willing to help you with these kinds of matters...
'Generally' because the banks like catching fraudsters!
I hope everything works out proper for you. Don't let this get your New Years down... Happy New Years all!