1. Turn your Sony VGNCR420EP laptop over.
2. Find the laptop battery release button lock for your Sony VGNCR420EP laptop.
3. Now that your Sony VGNCR420EP 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 VGNCR420EP battery is removed, grab your replacement Sony VGNCR420EP battery for installation.
6. Insert the battery into the slot. Push the Sony VGNCR420EP battery towards the laptop and secure it in place.