Hello- I recently sold my old 2.4GHz i5 15" 2010 MacBook Pro on ebay. The buyer claims he is not satisfied, and wants a return, as it is a "core 2 duo" machine and does not have multiple cores... What I sent him was exactly what I described, a core i5 machine from 2010... What do you advise I do? I've already sent off an email saying to go and check About This Mac and the sort. I really have no clue what to do at this point. Thanks!