A PC or laptop that won't turn on can be a traumatic experience, particularly if you rely on it as your primary device.
However, it's important to take a deep breath and run through what the potential causes might be. If it's one of the six below, we've included information on how to hopefully get it up and running again.
Method 1. Check the power supply
This is one of the most common problems. There are various things that can go wrong, from using the wrong laptop power supply (delivering the wrong voltage) to a blown fuse in the plug.
So check that the adapter is indeed the correct one for your laptop and is delivering the right voltage and amps. Stickers or markings on both the power supply and laptop should confirm this. Some third-party chargers also output power at a speed that is only equivalent to what your device requires to run. Older devices in particular can lose significant amounts of battery when in sleep mode, and may therefore not turn on if one of these chargers are used.
Many laptops – especially from the same manufacturer – use the same size plug, and if you own more than one, it’s not too difficult to plug in the wrong power supply, which might provide a different voltage or not enough current.
If it's the correct charger, next check the fuse in the plug. Use a screwdriver to remove the fuse and swap it for one that’s known to be good. If you have a spare power cable that will plug into your power supply, this is a much quicker way to test that it isn’t the fuse at fault.
Check over the wire itself, as power supplies get beaten up, especially if you carry them everywhere. Weak points are at the ends where it joins the black brick and at the plug which connects to the laptop. If you can see the coloured wires inside the black outer protection, it could be time to buy a new power supply unit (PSU).
If you're having problems with a touchpad, it's worth checking out our guide to fixing a cursor that's not moving.
PC power supplies can also be problematic. It's unlikely you'll have a spare to install and test, so first check the fuse in the plug. There's also a fuse inside the PSU itself, but it will require you to take it out of your PC (no mean feat) and then remove the metal case to check if that's the problem.
One of the most common PC power supply issues is that the PC will turn off unexpectedly rather than fail to boot up at all.
If the LED is on showing that power is reaching it, make sure the power button in your PC case is properly connected and working.
You can short the appropriate motherboard pins together (check which ones in your motherboard manual) to eliminate the power button from the equation. Some motherboards even have a built-in power button.
Method 2. Check the screen
Try disconnecting any external displays including projectors and monitors to make sure they're not stopping your laptop from booting into Windows.
If your computer's power LED lights up and you can hear the hard disk or fan(s) whirring, but there’s no image on the screen, then make the room dark and check that there isn’t a very faint image on the screen.
It’s easy to think a laptop isn’t booting when in fact, it’s the screen that’s the problem.
If there is a faint image – maybe the Windows logon screen – then the inverter could have failed, but this applies only to old laptops before LED backlights came along.
Replacing an inverter is difficult and it’s crucial you buy the right replacement part. As inverters aren’t exactly cheap, you can’t afford to get it wrong. It's a job best left for the professionals, but as your laptop is likely to be old, it's probably time to buy a new one.
If your laptop appears to be booting fine, but there’s no image at all, the LCD panel could be at fault. Replacing a laptop screen is possible, but difficult, and screens can also be costly.
There isn't much you can do to fix a broken PC monitor, but it's easy - or easier - to swap the power cable and video cable or even the whole monitor to see if that's the reason your PC won't boot.
Method 3. Unplug and removable USB drives or memory cards
Assuming everything is ok with the power supply and screen, your computer may be getting stuck before it loads Windows.
A classic culprit here is a USB drive or memory card left inserted into a USB port or card reader. Typically you'll see an error message such as "Operating system not found" which can lead to unnecessary panic.
For the majority of the time, it means the BIOS is set to try booting from removable storage drives (including cards) before the internal hard drive.
It could also be a disc left in the DVD or Blu-ray drive, so check those too.
Method 4. Try a rescue disc
If none of the above has worked, you can try booting from a rescue disk or USB drive.
If you have one, the Windows DVD can be used, but otherwise you can download (using another computer – obviously) a rescue disc image and either burn it to a CD or DVD, or extract it to a USB flash drive. You can then boot from this and attempt to fix the problem with Windows.
If a virus is causing the problem, use a rescue disc from an anti-virus provider as this will include scanning tools which can find and remove the malware.
Method 5. Boot into Safe Mode
Even if you can’t boot into Windows, you might be able to get into safe mode. Press F8 as your laptop is starting up and you’ll get a menu offering to boot into Safe Mode. Here's how to enter safe mode. That won't work in Windows 10 though, as you need to be in Windows before you can get to safe mode. In that case, you'll need to boot from a rescue disc or drive as described above.
If you can enter safe mode, you might be able to undo any changes that caused your laptop or PC to stop booting. You could try uninstalling any new programs that you recently installed, uninstall a driver that was recently updated, or create a new user account if the account is corrupt.
Here’s a more detailed guide on how to fix a corrupt user profile.
If you see an option to repair your computer, try that.
Method 6. Check for faulty or incompatible hardware
If you’ve just installed some new memory or another piece of hardware, it might be preventing your computer from booting. Remove it (reinstalling the old memory if necessary) and try again.
If your motherboard has a LED readout showing POST codes, search the manual or online to find out what the code shown means.
Often it can be tricky to get a newly built PC to boot. The best tip here is to disconnect everything except the bare minimum needed to boot to the BIOS:
- CPU (with heatsink attached)
- Graphics card (if there's a graphics output on the motherboard, remove any plug-in graphics cards)
- One stick of memory (remove any others, and leave the single stick in slot 0 or whichever the manual recommends)
- Power supply
All other hardware is unnecessary: you don't need a hard drive, optical drive or any other components for the PC to start.
Common reasons why a newly built PC won't boot are:
- Power leads improperly attached to motherboard. If your board has an extra 12v socket near the CPU, ensure the correct lead from the power supply is attached in addition to the large 24-pin ATX connector.
- Components not installed or seated properly. Remove memory, graphics card and CPU and reinstall, checking for any bent pins on the CPU and CPU socket.
- Power button wires connected to wrong pins on motherboard.
- Power cables not attached to graphics card. Ensure PCI-E power leads are correctly connected if required by your GPU.
- Hard drive connected to the wrong SATA port. Ensure the primary drive is attached to a SATA port driven by the motherboard chipset, and not a separate controller.
Sometimes the reason a PC won't boot is because a component has failed and there’s no easy fix. Hard drives are a common issue. If you can hear a regular clicking, or the drive spinning up and the powering down over and over, these are signs that it’s broken.
Occasionally, people have found that removing the drive and putting it in the freezer for a couple of hours (in a freezer bag) does the trick.
However, this is usually a temporary fix and you should have a second drive on hand to quickly back up or copy any files off the drive that you need.
If you can’t get the drive going again, it’s time to start afresh with a new hard drive. In fact, you're better off buying an SSD. Hopefully you have a recent backup of all your important files!