My Computer Won't Turn on
There's an old saying that technology is great--when it works. Sometimes the simplest things can result in the biggest headaches, especially where computers are concerned. Failure of a computer to start is a "headache" problem because the technological symptom doesn't give you a whole lot of ideas about what is wrong with the computer. The good news is that you at least can separate start failures into power and hardware issues, and that you can troubleshoot these areas step by step.
Plug a lamp or other electronic device into the same power outlet into which your computer has been plugged. If your device powers up, you know right away that you have power from the wall and that the power problem is in the computer.
Make sure that your power strip, surge protector or wall switch is in the On position if your lamp test shows no power. You wouldn't rob your computer of power this way intentionally, but it's easy to knock a switch and not even realize it happened.
Check the fuse or circuit breaker for the electrical outlet if no devices work and the switches all are in the On position as needed. Replace the fuse or flip the breaker if needed.
Make sure that all of the computer's power buttons are in the On position. There usually is one on the front and back of the tower.
Make sure that the power-supply voltage switch is configured correctly. The voltage switch is a small switch on the back of the power supply that, if in the wrong voltage setting, won't allow the computer to turn on.
Check that the power supply is functioning with a multimeter or power-supply tester. The power-supply tester is much safer because it is automatic. Replace the power supply if it's bad.
Look for any disconnected power cables. Even if you didn't purposely disconnect anything, cables can work lose over time due to the vibrations from the computer parts and from the tower's getting accidentally bumped now and again.
Check the configuration of the computer. If you've been working on the computer yourself, you might have messed up a setting involved with startup.
Test the motherboard. The motherboard is like the brains of the computer and may not be processing startup information properly.
Listen to the beeps you hear if your computer is turning on momentarily but then shutting off. Jot down what you hear as best you can and then refer to the beep code for the manufacturer of your motherboard in order to diagnose the startup problem.