Ive need to take my 10 Month old iMac into the Apple shop where I bought it from for a repair , ( screen problem ) Ive never had to take my Mac in for repair before so I really don't know what to do in the way of '' preparing '' it to be looked at by the technicians , I really would not like some one to play around with say my photo collection, Etc ( I have a full system backup on an external HDD ) , what would recommend I do to '' prepare '' the iMac ?