Why won't my pc turn on

If any lights are blinking and the pc is normally connected to the plug. you have to measure the voltages at the atx port in the motherboard. usualy the problem is just bad power supply (that inside the pc) you have to make sure that you have PS signal (usually the green wire the black is GND) have to be 5V once the machine is plugged in. Once you press the power button must turn 0V if it does, you have to make sure that you got 5V at the gray wire (PG) and also make sure that all the voltages of the atx are present 3,3V(orange),5V(red),12V(yellow). if you dont got any voltage at the gray while the machine is off you have propably bad PSU. there are many thigs which could be the actual culprit. Please be exrimely carefull if you arent expirienced using a multimeter DONT TRY IT. electricity is extreemly dangerous. you could harm youreslf or your equipment or even both.