1. Turn your Compaq 2120LA laptop over.
2. Find the laptop battery release button lock for your Compaq 2120LA laptop.
3. Now that your Compaq 2120LA laptop battery is unlocked, find the battery release button down.
4. Holding the laptop battery release button, gently pull your battery away from the laptop.
5. Now that your Compaq 2120LA battery is removed, grab your replacement Compaq 2120LA battery for installation.
6. Insert the battery into the slot. Push the Compaq 2120LA battery towards the laptop and secure it in place.