Laptop won't boot

I have an HP Compag NC6400 laptop. using last night with no problems.
Standard shutdown. This evening powered up and nothing. No BIOS screen, no
HDD activity, nothing, just blank, black screen.

No Spare RAM to test but removed RAM and powered up to check for POST beep.
Nothing but then not sure if on this model to expect something. HDD OK as
removed and checked via USB test rig by desktop PC. Disc readable and
contents as expected.

Am I looking at faulty RAM? or something more serious like blown
motherboard. Appreciate any input as to what additionally to do/check for to
resolve.