2002 Saturn SL1, 72K miles. Hasn't been driven in

Vehicles have a varied number of electronic control modules for the engine , ABS , air bags , body control , anti- theft , keyless entry etc.. When the vehicle is parked ,key off these modules are suppose to enter into sleep mode. Some times they don't go to sleep , bad module ,wiring problem or a light is staying on. How to Find Parasitic Battery Drain

Your ignition could be stuck. That happened to me on my 2002 Chevy Malibu with 150,000 miles on it. The ignition sometimes gets stuck and freezes up. You'll have to pull it out and put a new one in. You can use the new key or have it re keyed to fit your old keys.

if your ground is bad or has a short the cable then acts a reverse deducter when car is off try changing the ground wire or yhe light switch

I have the same problem. Usually I notice that somehow my trunk is open. Even if it is slightly open the light in there is on and the battery drains. I have also had it happen when there hasn't been anything on or open. I have to take it to the dealer at some point but for now I am replacing the battery because it is competely drained and I can't even get a jump to charge it. :(

the best way to determine the cause of the noise is to remove the drive belt and start the engine for a few minutes. if it is in the drive belt components then the noise will cease. if not then the noise will remain.

Purchase a OBD2 code reader for $50-$100. Scan for codes and let me know what Diagnostic Trouble Codes are active.

alternator problem ,start engine the remove a battery terminal if engine stops renew the alternator

Did you check the alternator? if it is faulty the car will drain all the power from the battery until it goes flat

check the battery cables and the battery if it is weak or dead this will happen. try jumping the car off with another car. be sure to stand back once you attach the neg. side

yes it sounds like the alternator