if it was tested and worked fine for you,it should work fine for the buyer as well.i wouldnt offer a refund.maybe its his system not reading the disc,that wouldnt be your fault.or maybe he has a case of buyer remorse.i have had that happen to me a few time on ebay and here on digitalpress(norkusa),so i say to tell the buyer it was tested when the item left your hands and maybe he has a problem with his system.