Disconnect the AC Adapter from the computer. Power on the system and continuously tap F1 to enter the BIOS. If you receive a general help window, press enter to continue. Use the right arrow key to select the configuration menu. Use the down arrow key to highlight power menu, and press enter. The power sub menu will be displayed. Use the down arrow keys to highlight the disable built in battery option, and press enter. Assure that yes is highlighted and press enter again to power off the system. Allow your system three to five minutes to cool before you open up the cover. Place the unit upside down. Slide the External Battery lock to the unlocked position. Slide and hold the External Battery release latch to the open position. Slide the External Battery out of the chassis. Turn the system over. Insert a straightened paper clip into the release hole of the SIM card tray. Pull the tray from the slot and leave it out until servicing is complete. Place the unit upside down. Loosen the eight captive screws that secure the base cover. Use a plastic pry tool to disconnect the clips along the rear of the cover. Then continue prying along the edges. Warning: make sure not to damage any ports or boards. Lift the front of the base cover to pivot it free of the securing clips. Align the base cover with the ports of the system. Press along the edges to secure the locking clips. Make sure the cover is seated correctly. Tighten eight captive screws. Turn the system over. Insert the tray into the slot until it clicks into place. Place the unit upside down. Align the External Battery with the battery bay. Slide it into position until it latches. Connect the AC adapter to the system. Turn on the computer to automatically enable the internal battery.