It's in the top post in this forum so a short version. Power off, remove AC, battery, press and hold the power button 60 seconds, release, battery then AC and re-test.
If not, let's hear more about the age of the laptop, etc.
Hi.. i use sony vaio laptop. i put win 8 , partitioned one disk from local disk c. then sshut it down. again i turn on, screen is black. wat will be the prob????? may be hardware prob or hard disk prob????