Well your computer should shut down when unplugged or else that would be something if it stayed on with no power and you somehow defied the laws of physics and had a free energy source in your PC.
Then you say it won't turn back on.
Then you ask IN GREAT BIG CAPS how to shut the power light off?
I have no idea what your question is or what the problem is. You can try asking again in a proper way and actually explain what happened.