People just stop it already.
Anyway something to be learned from the OP's experience put some tracking software on the computer if you sell one. Also Paypal or Western Union is probably the best because even as a buyer what's to stop people from claiming that you stole it and using lojack software to find and report you? You could get screwed on either side of a computer sale. Better to have 3rd party evidence of the sale even if it means sticking your behind out to Paypal.