First try taking the battery out and make sure the AC adapter is disconnected from the laptop & electrical outlet. Press the power button 10 times, and on the 11th time hold the power button down for around 30 seconds. After letting go of the power button, plug the AC adapter into the laptop and the electrical outlet (leave the battery out for now), and try starting it up.
If this doesn't help try holding down the F8 key while the laptop is off, and while you're holding it down press the power button to turn it on, if the advanced boot options menu comes up try booting to Safe Mode