Disengage two connectors on a small circuit board on the bottom of the 2nd hard disk bay and lift the screened cable off the bay.
Remove two 6.5mm black screws. (On reassembly it's important to put these screws back in the right holes otherwise the front cover of the laptop won't fit.
Gently lift the motherboard from the right hand edge, first disengaging the audio sockets and volume control from the lower shell, then the connectors from their openings in the left hand side. You can now remove it completely.