Number 1.
Ther is no CPU button, I believe you are referring to the Power Button.
Number 2.
This could mean many things, Your PSU could be dead, your CPU could be dead, your motherboard could be dead.
By the sounds of things though its probably your PSU or Motherboard, please post the specs of your PC Including the PSU wattage, make and model, and the Motherboard Make and model.