Question: why is my battery not holding a charge?

HI, BEST WAY TO FIND YOUR BATTERY DRAIN IS TO DO A CURRENT DROP TEST. DISCONNECT NEG. BATTERY TERMINAL ATTACH A TEST LIGHT BETWEEN TERMINAL AND BATTERY POST,WITH ENGINE OFF TEST LIGHT SHOULD BE VERY DIM IF BRIGHT START REMOVING FUSES ONE BY ONE TILL THE LIGHT GOES DIM.HOPE THIS HELPS

Have alt. bench tested for possible internal failure. Was problem with battery drain present before alt. replacement and also when did the rear windows become inoperative?You say when car is off it's dead. Safe to assume you mean no headlights , door chime with key in ignition ETC.? After you shut car off and it's 'dead' WHAT do you do to restart it?