Hi, I have a MBP which I purchased in August of 07. I have never had a problem with it. However, recently I have noticed that the battery is discharging when the computer lid is shut and the laptop is not plugged in. This weekend I left the laptop unplugged with a full charge and when I arrived home, the battery was around 17%. Also, the health of the battery is 75%. Is this normal? Is there anything I can do to fix it?