Make sure you have nothing plugged into the USB ports or a DVD/CD in the player.
Try this
1. Unplug AC adapter from laptop.
2. Remove the battery.
If the battery is not removal then your only choice is to sit a couple of weeks without being plugged in to kill it.
3. Press and hold the power on button for 1 full minute.
Yes, many machines only require 10 or 15 seconds but this reset instruction is generic and I have found people hold the button for 9 or 14 seconds so let's write the full minute.
4. Let go of the power on button.
5. Slip in the battery pack.
6. Plug in the power to the laptop and to the wall.
7. Do not plug in any other devices.
Try the power on button!
If that does not work try it again without putting the battery back in. If either of these works, it is an indication that you have a bad battery. Do not use it with the bad battery install.
If that does not work check the lights to see if any of them are blinking in a pattern. Sometimes you can get a diagnostic from a blinking caps lock or some other light. HP has a very good post code thru its cap locks. The link below shows what they mean. It will help get an idea of what to look for.
http://h30434.www3.hp.com/t5/image/serverpage/image-id/5215i44093B88076B3876/image-size/original?v=mpbl-1&px=-1
Check the power jack in the puter and see if it is loose. They have a bad habit of becoming detached from the motherboard.
If no lights are blinking or other wise you might have a dead AC adapter. Find someone with a DVM and see if you can check it. If you have no experience with DVM get someone with experience to do it. You can cause damage if you do it wrong.
If none of this works then you probably have a bad motherboard.
