First reset the latop by pulling battery and unplugging. Let it sit minimum of 2 mins to let capacitors drain. Then put battery back in then plug in wall. Will it power up now? yes - great. No -- check your manual to see if there is another way to reset.
If resetting does not work then start pulling parts. Anything that is externally attached, then memory, then any internal PCI cards (like wireless card), then hard drive. You are looking for the laptop to start up to the point where it complains that parts are missing. Then add parts back in 1 at a time until it fails again. Then swap out that part.