Dell 1440, M792N, PP42L To remove the battery:

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Using Your Inspiron™ Laptop
WARNING: Before you begin any of the procedures in this section, follow the safety
instructions that shipped with your computer.
WARNING: Using an incompatible battery may increase the risk of fire or explosion. This
computer should only use a battery purchased from Dell. Do not use batteries from other
computers.
WARNING: Before removing the battery, shut down the computer, and remove external cables
(including the AC adapter).
To remove the battery:
Shut down the computer and turn it over. 1.
Slide the battery release latch to the side.2.
Slide the battery away from the battery bay.3.
To replace the battery, slide it into the bay until it clicks into place.