Your going to have to give us the model number of your PB laptop to stand a chance of getting specific advice.
However, as with many laptops that don't boot up, locate the battery on the bottom, unscrew whatever screws hold it in place and remove the battery. Then make sure the power cable is removed so that there is no power running to laptop at all and whilst in this state, hold the power button down for 30 seconds.
Then refit the battery and next, plug power cable back into computer and mains socket on wall.
Hopefully, this will allow you laptop to boot up properly.
If this does not work, try giving us some more information and we may be able to help further.