Did he opened the CD already? If not, ask him to send it back first and then you give him his money back. You can always exchange responses through Ebay, remember? That way both camps will have proofs of conversation and agreement. If he insists to do it his way, let him do it. You can defend yourself once he posts a negative feedback. Besides, there is nothing much he can do. PayPal do not give refunds to CDs, so it s always the buyer who s at the losing end. And be brief and clear when posting ads. Sometimes, people just buy things and are too lazy to read and analyze.
let him leave it, ebay also give u a chance to explain ur side on ur ebay profile....also u can make a complaint to ebay which i highly recommend I m sure they can block him