Diagnosing a machine's sickness

Hello.

My HP Pavillion laptop suddenly just shut off while I was using it, and it won't turn on, except for a very brief, and small flash of light from the light under the power button, and the side.

I've tried to drain any kind of static energy by holding down the power button, and repeating with and without the power chord, and the battery of the laptop with no success.

What could be wrong with my laptop? How could I fix it?