This article only applies to: Travelmate P645 series
The notebook battery is disabled if the HDD and memory compartment door is not properly secured. This is a safety feature and happens when the screws that secure the door are not fully tightened.
Tighten the 4 screws that secure the HDD and memory compartment door. If you are unable to tighten the screws or you are still having problems, please contact Acer support