If you press the power button on your computer, and it doesn't turn on, it could be that your motherboard is damaged. Your motherboard can incur damage in several ways.
Dropping your computer's case can warp and crack the motherboard. If the board is bent or scratched during installation, this can also cause it to fail.
A computer case that has insufficient cooling or is in a hot environment can overheat. This can cause the motherboard to warp and some of the parts to melt.
A lightning storm can hit an electrical pole and cause a surge of power to flow through your residence's electrical system. The surge can burn and melt a computer that's not equipped with a surge protector.
A rapid change in temperature can cause the internal components of a computer to permanently warp, rendering them inoperable. This happens a lot with laptops: People leave their laptops in their cars during a heatwave or snowstorm, then they bring their laptops into a climate-controlled environment.
Faulty Power Supply
A damaged or improperly manufactured power supply can send too much electricity to a motherboard, frying its components.