goingalong

I use this old machine for MCU programming for which it is ideal. The problem is that the only way to get it to permanently turn off is to remove the charger Jack (no battery is fitted). When I shut down the OS the machine closes down then comes right back up into the boot sequence - unless the lid is shut. The power switch has no effect even after holding it down for a long time. Also no lights show on the power board (num-lock, caps etc). I have changed the power switch board and it's cable and this had no effect. Is my mainboard busted, or is there another setting somewhere, or is it the absence of a battery?