The motherboard is protected by the steel frame, with the back facing the screen. You can lift the entire frame without detaching many cables, only the webcam and Wi-Fi card.

Remove the five circled screws to release the motherboard. Then slide it straight out of the frame, releasing the Ethernet and USB ports.

The center screw is the BIOS write protect screw. Note that the pad has two raised quarters: The screw shorts these together to enable write protection. Do not replace this screw if you want to be able to flash the board with an un-restricted EFI image.