If your computer won't boot, try these six things.

If your computer is your primary means of communication and it suddenly stops working, it can be very upsetting.  

But before doing so, it's important to take a deep breath and consider what might be causing this. If it's one of the six listed below, we've included some troubleshooting steps to take in the hopes of getting it back up and running.  

1 Verify the source of power.

Laptops

This situation has many potential pitfalls. It's possible that you accidentally used the charger from another laptop. It's not necessarily the correct connector if the connector itself fits. There is a difference in the voltage that different laptops use. The power supply may have the right voltage, but it may not supply enough amps to run your laptop and charge its battery.

Make sure the laptop's power supply matches the model and is producing the required voltage and current. Both the adapter and the laptop should have stickers or markings to verify this.

Make sure you're plugging the charger into the correct USB port on your laptop if it charges via USB-C and it's a relatively new model. Not just any USB-C power supply will work for some laptops; in particular, Huawei MateBooks are picky about having the official charger.

In that case, double-check the plug's fuse to make sure you're using the right charger. Take the fuse out with a screwdriver and replace it with a good one. You can quickly determine if the fuse is the problem or not by plugging in a different power cable to your power supply.

If you're constantly dragging around your power brick, it's a good idea to give the cable a once-over. The ends where it connects to the black brick and the point where the plug connects to the laptop are the two weak points. A new power supply unit (PSU) might be in order if the colored wires inside the black casing can be seen.

Check out our guide on how to fix a touchpad cursor that won't move if you're having issues.

PCs

Similarly problematic are PC power supplies. Since you probably don't have a spare on hand, you should start by checking the plug's fuse. The power supply unit (PSU) itself may have a blown fuse, but diagnosing that issue will necessitate removing the PSU from your computer (a pain) and then the metal case (also a pain).

The unexpected shutting down of a computer, rather than its inability to start up at all, is a common symptom of a faulty power supply in a computer.

Verify the power button in your PC case is connected and working if the LED is lit, indicating power is reaching the power supply.

If you want to disable the power button, you can do so by shorting the appropriate motherboard pins together (you can find out which ones in your motherboard manual). Additionally, some motherboards include an on/off switch on the board itself. Consequently, remove the computer case's side and inspect it for one.

2) Look at the monitor.

Laptops

Make sure there isn't a very faint image on the screen if the power LED comes on and you hear the hard disk or fan(s) whirring but there's no visible image on the screen.

The failure of the screen backlight can be mistaken for a non-booting laptop.

Inverters, used by older laptops without LED backlights, can fail.

The inverter is a complex piece of equipment, so it's important to get the right replacement part. Inverters aren't cheap, so you can't afford to make a mistake. It's best to have a pro do it, but since your laptop is probably quite old, you should probably upgrade anyway.

A faulty LCD panel could be the cause of a seemingly working laptop that displays nothing on the screen after booting. Screen replacement on laptops is possible but not easy, and screens can be pricey.  

However, before reaching that conclusion, you should make sure that no external displays (such as projectors or monitors) are preventing your laptop from entering Windows.

It's possible that the Windows login screen is displaying on a second screen that is turned off, leading you to believe that either your laptop or Windows is malfunctioning.

PCs

If you can't get into Windows, but the monitor still turns on and displays everything else fine, try swapping the power cable, the HDMI (or DisplayPort) cable, or even the monitor itself to see if that's the problem.

Take out any memory sticks or USB drives and disconnect them.

Assuming the power supply and display are fine, the issue may lie in the time between when you turn on the computer and when Windows actually loads.

A common cause of this problem is a USB drive or memory card being accidentally left in a computer's USB port or card reader. Error messages like "Operating system not found" are common and can cause undue stress.  

Typically, this means that the BIOS is configured to first try booting from external storage media, such as a card, rather than the primary hard drive.

You should also check the DVD or Blu-ray player in case a disc has been accidentally left inside.

4. Use a safety disc

Booting from a rescue disk or USB drive is an option if none of the preceding have been successful.

In the absence of a Windows DVD, a rescue disc image can be downloaded (obviously from another computer) and used to create a bootable CD/DVD or USB flash drive. In this way, you can use it as a starting point and access Windows repair tools.

Make use of a rescue disc from your anti-virus provider if you suspect a virus is to blame; this disc will contain scanning tools that can identify and eliminate the virus.

5 Start up in Safe Mode

You may still be able to boot into safe mode even if Windows fails to load. In order to boot into Safe Mode, press F8 while the laptop is starting up. How to Switch to Safe Mode However, in Windows 10, that won't work because you must first be logged into Windows in order to access safe mode. To do so, boot from a rescue disc or drive as explained above.

By booting into safe mode, you may be able to roll back the changes that prevented your laptop or computer from starting up normally. If the account is corrupted, you can try to uninstall any recently installed programs, roll back any updated drivers, or create a new user account.

A more in-depth explanation of how to restore a damaged user profile is provided below.

Check for a repair option on your computer and use it if possible.

Search for broken or incompatible hardware

Your computer may be unable to boot up properly if you have recently installed new memory or other hardware. Take it out (and put back the original memory if that's what you did) and try again.

LED readouts on some motherboards display POST codes; consult the user manual or go online to learn what each code means.

A freshly built computer can be difficult to get to boot. The best piece of advice is to remove everything from the system except what is required to enter the BIOS. To get started, you need only a

• Motherboard
• Central Processing Unit (with Heatsink)
• Remove any external graphics cards if your motherboard already has a video output.
• Remove all other memory sticks and place the lone one in slot 0 or the location specified in the user manual.
• Power generation
• Monitor

You can start up a computer without a hard drive or any other external hardware.

Most often, the following causes a brand new computer to fail to boot:

• Improper connection of power cables to motherboard In addition to the main 24-pin ATX connector, some boards also feature a smaller 12-volt socket near the CPU; this socket must have the appropriate cable attached.
• Improper assembly or seating of parts Take out the CPU, memory, and video card, and then put them back in while checking for bent pins.
• Connecting the wires for the power button to the wrong headers on the motherboard
• The video card's power cables are missing. If your GPU needs them, check that the PCI-E power cables are connected properly.
• Mismatched SATA port and hard drive Make sure the primary drive is connected to a SATA port managed by the motherboard chipset and not a third-party controller.

There are times when a PC won't boot because a component has failed and cannot be replaced. Disk failure is a common occurrence. The drive is broken if you can hear it clicking on a regular basis or if it keeps powering up, spinning, and shutting off.

Some have reported success after removing the drive and freezing it (in a freezer bag) for a few hours.

Having a second drive on hand to quickly copy or back up any files you need off the first is a better long-term solution.

If you are unable to get the drive to work again, you will need to replace it. In fact, a solid-state drive (SSD) is the way to go. Have faith that you have a recent copy of all your crucial data.

Here's how to schedule Windows 10 shutdown so that your computer turns off at a specific time.