1. Turn your Compaq 2135AC laptop over.
2. Find the laptop battery release button lock for your Compaq 2135AC laptop.
3. Now that your Compaq 2135AC 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 2135AC battery is removed, grab your replacement Compaq 2135AC battery for installation.
6. Insert the battery into the slot. Push the Compaq 2135AC battery towards the laptop and secure it in place.