Have you tried a power cycle.
Remove both the battery and AC Adapter. Hold the power button down for 10 seconds. reconnect the AC ONLY and attempt to power on the machine.
If this fails then you are looking at a problem with your PCB (power control board) if you are in warranty i suggest you contact HP. If you are out of warranty contact HP and ask whether your PCB is On-Board or a daughterboard/sub-assembly. This will then give you indicative costs of replacing the component.
I would say 9/10 if its onboard you are better off purchasing a new laptop with a new warranty as spare parts in the IT Retail industry only carry a 90 Day warranty.
KAVO
