Hi,
Are there any lights on the laptop? Remove the battery and AC adapter then press and hold the power button for 20 seconds. Plug just the AC adapter in and try to boot up the laptop. If it doesn't turn on but there's light on the laptop, connect an external monitor and see if you'll get any display from it because if you do the problem is within your built in display.
If there's no light what so ever on the laptop, try using another AC adapter that's the same with yours and see if you'll get power out from it. Remove the battery first when you do this and try powering it on.