- Turn off the computer,
- Take the battery out
- Take out the power supply
- Push the power button down for 30 seconds.
- Reconnect power supply leave battery off
- Attempt to boot
- If ok refit battery
Something else to try if you think its booting but nothing on screen is to cycle through the buttons which change from screen to external monitor (Fn (F5? blue square) or attach latop to external monitor or TV to check if screen failure.