Peal off the rubber feet by hinges (yellow squares in previous step)

This should allow you to remove the 11 remaining screws (2 un battery compartment, 2 under rubber feet and 7 just on bottom of laptop).

With the laptop upside down on desk the back plastic cover comes off leaving all the PCBs and speakers attached to back of keyboard/trackpad.

There are a series of plastic clips round the edge that are almost impossible to get off with out snapping, particularly if plastic is a bit old and brittle.

When unclipped you have to lift up slightly on one side and then sideways as the plastic cover hooks round the VGA connector on PCB. Once you've gone round and release the clips (I used small flat head screw drive but this probably wasn't be best tool as it had a tendency to snap plastic loops/hooks) then cover should lift off really easily.