1. Turn your Sony VGN-SZ120PB laptop over.
2. Find the laptop battery release button lock for your Sony VGN-SZ120PB laptop.
3. Now that your Sony VGN-SZ120PB 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 Sony VGN-SZ120PB battery is removed, grab your replacement Sony VGN-SZ120PB battery for installation.
6. Insert the battery into the slot. Push the Sony VGN-SZ120PB battery towards the laptop and secure it in place.