Volvo Repair: Dead battery, diagnostic computer, key hole

Question
My Volvo is a 2000 S-80 T6.  Due to non-use, the battery has died and I cannot open the doors with the key although it does set off the alarm system.  Is there a special procedure needed to access/replace the battery?  Can the vehicle be safely jump started?  Thanks for any help you can provide.  

Answer
The key remote will not unlock the doors but the the actual key SHOULD open them.  The battery is in the trunk anyways so you don't even need to get into the car to do it.  You can open the trunk manually with the key too.  If you get low enough and look at the underside of the handle you'll see another key hole that will allow you to acces the trunk.  Lift up the floor mat and under all of that the battery is under a bolted down cover.  It can be jumpstarted but it doesn't usually start up after being drained like that.  The computers are very sensitive to voltage and sometimes need a reset when they are powerd back up again.  To do this put the key in the door and then turn to lock, then unlock, then lock again in quick succession.  If it still fails to start, then it needs a hard reset from a volvo diagnostic computer and it may need to be towed to the dealer.  Hope that helps.

James