We have an old Mini Mac which we are going to use as the family itunes base. However when we plug our iphones in they are not recognised. The Mini Mac dates back to 2005 (pre iphone). It is OS x 10.3.9, 1.42GHz, Power PC G4. When we try to update it it says it is updated. What do we need to do for it to update to 10.5 or later?