bac cho e hoi la con sam sung forcus truoc ban e no chay rôm w7.8 cua lumia 800 nhug e ko thich gio e muon quay lai rom goc cua may co dc ko? va cho e hoi luôn la e forcus co rom chinh hãng 7.8 chua hay chi co ban 7.5 thôi. may e cua nha mang at&t v1.3. nêu co the bac huog dan chi tiet e up rom moi, e chua up window bao gio chi so hong thôi. camon bac nhieu