1. Turn your Sony VGNCR420E laptop over.
2. Find the laptop battery release button lock for your Sony VGNCR420E laptop.
3. Now that your Sony VGNCR420E 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 VGNCR420E battery is removed, grab your replacement Sony VGNCR420E battery for installation.
6. Insert the battery into the slot. Push the Sony VGNCR420E battery towards the laptop and secure it in place.