dell laptop not posting

Hi,
my old dell laptop recently came up with blank screen and i didnt even hear the post
beep that it is starting up.  tried putting windows xp cd in it to see if it will boot to it and
no good as well.  Doesnt even show bootup menu which shows option to get into bios or to hit any F keys at startup.  I know if hard drive is bad it will still at least show bootup menu and then get error that no bootable device available.  I think motherboard is bad but just to be sure, are there any other tests i can try.  The power light goes on but thats it.  No hard drive light or any sounds or startup screens at all.  thanks.