General hint:- Be careful what you do, as some actions cannot be fixed.
Hint:
Disarming the bomb:
To disarm the bomb in Zeitel's room, set the left switch to #2. Next, set
the middle switch to #3. Then, set the right switch to #3. Wait until the
clock goes off, then set the left switch to #1. Open the case with the key
in it. Get the key and click "OK". Finally, exit the room.