Hp pavillion laptop attempts to but will not turn on

My hp pavillion 9620us laptop attempts to turn on, but immediately goes off. In its initial manifestation, led lights and fan came on, and the screen would show the windows logo (attempting to fast boot); then everything would shut off. This would happen with and without the battery installed.

After leaving the problem aside for perhaps a year, I searched the internet and learned about the forced reset--battery removed, power adapter disconnected and on button held down for up to 15 seconds. Needless to say, the battery by this time is probably discharged.

Currently, with the battery in or out and the power adapter connected or with the battery in and the power adapter disconnected, the laptop attempts to start with LEDs on (including the power on LED) for about 2 seconds, and the fan attempting to rotate. The battery charging LED and the ring LED where the power adapter plugs in remain lit if the power adapter is connected and the battery is in. If the battery is out, only the ring LED remains lit, and the battery charging LED is always off. With the power adapter disconnected and the battery in, the ring LED and battery charging LED are always off. Caps lock and num lock LEDs do not turn on.

I am not sure how to proceed troubleshooting this problem. Suggestions would be appreciated. The HP support web site does not help.

As of 9/25/2015, no solutions to similarly titled problems posted on CCM work for this failure.