Start with the power supply and connections

A computer that will not start almost always has a power problem first. Before you assume the motherboard or hard drive has failed, check whether electricity is actually reaching the machine.

Look at the back of your desktop or the side of your laptop. If you see a power light — even a dim one — the machine is receiving power. If there is no light at all, unplug the power cable from the wall outlet and plug it into a different outlet in a different room. Plug a lamp or phone charger into the original outlet to confirm that outlet works. If the outlet was dead and the lamp lights up, your computer may start now.

For laptops, leave the charger plugged in for at least 30 minutes before trying to power on. A completely drained battery can take time to accept a charge. For desktops, check that the power cable is fully seated in both the wall outlet and the back of the power supply unit — the large metal box inside the case. Push both connections in firmly.

Key Takeaways

  • A dead outlet or loose power cable causes most computers that will not start, so test the outlet with another device and reseat the cable before assuming hardware failure.
  • Laptops with fully drained batteries need 30 minutes of charging before they will respond to the power button.
  • A computer that powers on but does not display anything on screen may have a loose monitor cable or a failed display, not a failed computer.
  • If the power button does nothing and the outlet and cables are confirmed working, the power button itself or the motherboard may be faulty.
  • Desktops sometimes have a second power switch on the back of the power supply unit that must be in the ON position.

Check the monitor and display cables

Many people think their computer is broken when the real problem is that the monitor is not receiving a signal. The computer may be running fine inside the case while the screen stays black.

Look at the cable that runs from the back of your monitor to the back of your desktop computer. This cable is usually blue or black and connects to a port labeled HDMI, DisplayPort, DVI, or VGA. Unplug this cable from both ends and plug it back in firmly. Do the same with the power cable on the monitor itself — plug the monitor into a working outlet if you have not already.

If your laptop has an external monitor plugged in, unplug the monitor cable and look at the laptop screen directly. The laptop screen may be working while the external monitor is not. If the laptop screen is also black, move to the next section.

Try a hard restart and check for stuck power buttons

A computer that appears dead sometimes just needs to be forced to shut down and start fresh. On a desktop, hold the power button for 10 seconds without releasing. The machine should power off completely. Wait 30 seconds, then press the power button once to turn it back on.

On a laptop, hold the power button for 10 seconds. If nothing happens, try holding it for 15 seconds. Some laptops require a longer hold. After the machine shuts down, wait 30 seconds and press the power button once.

While you have the case open or the laptop in front of you, look at the power button itself. Press it gently a few times. If it feels stuck, loose, or makes a grinding sound, the button may be physically damaged. Dirt or liquid can jam a power button. If the button feels normal, move to the next section.

Look inside a desktop for loose parts

Desktop computers have internal components that can come loose if the machine was moved, bumped, or opened recently. A loose memory stick or graphics card can prevent the computer from starting.

Unplug the power cable from the wall and the back of the computer. Open the side panel of the case — usually held by two thumbscrews or a latch. Look inside at the long green circuit board (the motherboard). You should see one or more rectangular sticks of memory plugged into slots near the processor. These sticks should be pushed all the way down and locked in place by clips on both ends.

Push down firmly on each memory stick until you hear or feel a click. If you have a graphics card — a large card plugged into a slot on the motherboard — push that down as well. Close the case, plug in the power cable, and try to start the computer. If it still will not start, leave the case open and move to the next section.

Test the power button circuit and motherboard

If the power button does nothing and the outlet, cables, and internal connections are all confirmed working, the power button circuit or motherboard may have failed. On a desktop, you can test whether the motherboard is receiving power by looking for lights or fans that spin when you plug in the power cable — before you even press the power button.

Unplug the computer. Look at the motherboard for a small light, usually green or red. Plug the computer back in without pressing the power button. If you see a light on the motherboard, the power supply is working and the motherboard is receiving power. If you see no light, the power supply itself may have failed.

If the motherboard light is on but the power button still does nothing, the button circuit or the button connector may be faulty. The power button connects to the motherboard through a small plastic plug with two or four pins. This plug can come loose or be plugged into the wrong pins. Check your computer's manual or search online for your exact model to find the correct pins for the power button connector. Reseat the connector firmly.

Know when to stop and seek repair

If you have tested the outlet with another device, reseated all cables and internal connections, and confirmed that the motherboard is receiving power, the problem is likely a failed power supply, motherboard, or power button circuit. These are not repairs most people do at home.

At this point, contact the manufacturer if your computer is still under warranty, or take it to a local repair shop. Provide them with the steps you have already taken — this saves them time and may lower the repair cost. If the computer is very old, the repair cost may exceed the value of the machine, and replacement may be the better choice.

Frequently Asked Questions

My computer powers on but the screen stays black. Is it broken?

Not necessarily. Check that your monitor is plugged in and that the cable from the monitor to the computer is fully seated on both ends. If an external monitor is connected, unplug it and look at the laptop or desktop screen directly. The monitor cable or monitor itself may be faulty, not the computer.

My laptop won't turn on and I have not used it in months. What should I do?

Plug in the charger and leave it connected for at least one hour. A battery that has been fully drained for a long time needs time to accept a charge before the laptop will respond. After an hour, try pressing the power button. If nothing happens after two hours of charging, try a hard restart by holding the power button for 15 seconds.

I hear the fan spinning but nothing appears on the screen. Is the computer working?

The computer is likely running, but the display is not working. Check the monitor cable and power, and make sure the monitor is set to the correct input. If you have an external monitor, unplug it and check the laptop screen. If the laptop screen is also black, the graphics card or display port may have failed.

Can I fix a computer that won't turn on myself?

You can test the outlet, reseat cables, and check internal connections like memory sticks. These steps are safe if you unplug the computer first. If none of these work and the motherboard is receiving power, the fault is likely inside the power supply or on the motherboard itself, which requires professional repair.

My power button is stuck. Can I fix it?

If the button feels jammed, try gently working it back and forth. If dirt is visible, use a dry brush or compressed air to clean around the button. Do not use liquid. If the button remains stuck or broken, the button itself or the button circuit may need replacement, which a repair shop can handle.