My computer keeps crashing – what should I do?

Dealing with a computer that constantly freezes is undeniably frustrating, especially when it happens while you’re gaming, editing photos or trying to get work done.

These freezes can be caused by a range of issues, including an outdated operating system, low disk space or even the presence of malware. On the plus side, there are several effective ways to troubleshoot the problem and get your computer running as it should.

Below, we run through some potential reasons why your Windows PC or Mac keeps crashing – and how to fix the problem for good.

Get tech confident for less

Solve your tech issues and get expert buying advice by chatting to our support team as often as you need. From only £4.99 a month.

Join Which? Tech Support

Cancel any time

Already a Tech Support member? For more help and 1-to-1 technical advice, including buying advice, go to our Tech Support online booking tool.

How do I stop my PC from freezing?

'My three-year-old laptop keeps freezing at random. I could be working in a Word document or browsing the internet when it suddenly seizes up. I either have to wait (sometimes 15 to 20 minutes) for it to respond, or switch it off and reboot.

'Do you have any ideas on how I can stop it from becoming unresponsive?'

Which? Tech Support member

1. Update your operating system

Keeping your operating system up to date is one of the most effective ways to ensure your computer runs smoothly. These updates fix security vulnerabilities and add new features, plus they improve performance.

• On Windows 10 Head to Settings > Update and security > Check for updates. (Windows 10 users need to take action to continue to get security support – see what you need to do when Windows 10 loses security support.)
• On Windows 11 Head to Settings > Windows Update > Check for updates.
• On macOS Select the Apple logo > System settings > General > Software Update.

2. Download the latest drivers (Windows)

PC makers and component manufacturers release driver updates for hardware such as graphic cards, USB drives and chipsets. Keeping these up to date can resolve issues and improve both stability and performance.

To check for missing or outdated drivers, visit your computer manufacturer’s official website (for example, HP, Asus or Dell). If you built your own PC, go to the component maker’s website instead, such as Nvidia for a graphics card.

Navigate to the Support or Downloads section, then enter your computer or component’s model or serial number. Download and install all the latest drivers compatible with your operating system. It's also recommended that you install any available Bios updates (the Bios controls what your PC first does when you switch it on, such as checking and starting hardware and loading your operating system).

If you think you're due a PC upgrade, pick the right model and specs: see best laptops, best all-in-one PCs, and how to buy the best desktop PC.

3. Identify blue (now black) screen codes (Windows)

When Windows freezes completely and then crashes to the point where it has to restart or shut down, it often displays an error code. This used to be on a blue screen (known affectionately as the Blue Screen of Death, or BSOD), but the latest version of Windows 11 has changed this to a black screen.

These codes typically appear as 0x0000007E or IRQL_NOT_LESS_OR_EQUAL. They can be very useful in diagnosing why the computer froze or shut down, so make a note of the code and search for it on the Microsoft support site.

4. Scan for malware

Freezing can sometimes be a sign of malware, as malicious software often causes instability and places a heavy load on system resources. It can overuse the processor, memory and hard drive, making your computer unstable.

We recommend performing a full scan using a robust antivirus program to pick up any potential malware. (See also: signs your computer has been hacked).

Our expert guide to the best antivirus software will help you banish malware.

5. Check your computer’s memory, storage and temperature

On Windows, try this:

• Ram/Memory test Press Win + R, type mdsched.exe, and press Enter. Choose Restart now and check for problems to perform a memory test. Typically, if your PC finds issues, it normally points to a hardware fault with the Ram or a particular stick of Ram.
• Hard drive check Open File Explorer, right-click your system drive (usually C:), and select Properties. Go to the Tools tab, choose Error checking, then click Check. Windows will scan, analyse, and attempt to repair any issues it finds.
• Storage space Press Start, type Storage settings, and select the result. At the top, you’ll see how much space is used and how much is free (try to keep at least 15-20% free on your system drive). Windows will also show a breakdown of what’s taking up space, such as apps, documents, or pictures. You can then free up storage by deleting files or moving them to another drive or a cloud service. Also consider getting one of the best external hard drives to free up space.
• Check temperatures Download and install HWMonitor. Open the tool and check the CPU (your processor) and GPU (if you have one – this is a chip that handles graphics) temperatures. Ideally, under regular use, they should stay under 80°. If temperatures are high, it can cause freezing, throttling or unexpected shutdowns. If temperatures remain consistently high, try cleaning dust from the fans or improving airflow. You may also need to replace the thermal paste, which could require in-person tech support. You can use Which? Trusted Traders to find a good, local computer repair shop

On macOS, try this:

• Diagnostic tool Apple’s built-in diagnostics tool can detect hardware issues. Turn on your Mac, then immediately press and hold down your keyboard's D key as it starts up. Release when you see a progress bar or when you're asked to choose a language. When testing is complete, Apple Diagnostics shows the results, including a reference code which you can check on the Apple support site.
• Disk check Open Finder, then navigate to Applications and Utilities. Open Disk Utility, then select your main drive (usually Macintosh HD) and choose First Aid. This will analyse the drive and attempt to repair any faults.
• Storage space Press the Apple menu, select System Settings, then click General. Choose Storage, then click All Volumes. You’ll see how much space is used and how much is free (try to keep at least 15–20% free).

My home PC kept locking up, but now I know why

'Up until recently, I was experiencing increasingly frequent crashes on my home computer while gaming. Frustratingly, Windows wasn't even showing me a blue screen with an error code – it just froze without warning, forcing me to do a hard reset by holding down the power button.

'After discussing the issue with Which? Tech Support, it quickly became apparent that the crashes could be down to two factors. Firstly, my Nvidia graphics card drivers were outdated. Using Task Manager, I also discovered that playing newer games was using up a large amount of Ram on my ageing machine.

'In my case, the best option is to replace the PC entirely, which I’ll be doing right away. My current computer is underpowered for what I need it to do now. And since it isn’t compatible with Windows 11, it will become exposed to security risks once my extended Windows 10 licence runs out in October 2026.'

Tom Morgan, Which? senior digital content producer

6. Boot into Safe Mode

Booting your computer into safe mode loads the operating system with only essential software and basic drivers.

If a third-party program is causing the freezing, it shouldn’t occur in Safe Mode. Running in Safe Mode can also rule out a virus or malware as the root cause.

On Windows, try this:

1. Click on the Start Menu.
2. Press the Shift key and, while holding it down, choose Restart.
3. When your computer restarts, choose Troubleshoot > Advanced options > Startup Settings > Restart. Press the key corresponding to Enable Safe Mode (F4) and your computer will boot into Safe Mode.

If your device works normally in Safe Mode without freezing, restart the computer for it to go back to ‘normal’ mode. Then, disable all apps and services, and re-enable them one by one until the culprit is determined. To do this: 

• Press Win + R, type msconfig, and hit Enter. Go to the Services tab, check Hide all Microsoft services, then click Disable all.
• Switch to the Startup tab and click Open Task Manager. In Task Manager’s Startup tab, disable all apps and restart your computer.

If it runs fine, re-enable apps/services one at a time, restarting after each, until the crashing returns. Once the freezing returns, you’ll know which application is the culprit.

On macOS, try this:

1. Shut down your Mac.
2. Turn it back on while holding down the power button until you see Loading Options, then release it and choose Options > Continue.
3. Choose your startup disk and click Continue. Once logged in, your Mac will start up in Safe Mode.

If your Mac doesn't crash while in Safe Mode, restart it to return to ‘normal’ mode. Disable all apps and services, and re-enable them one by one until you know the cause.

To do this: 

• Press the Apple icon, then select System settings > General > Login items & Extensions. Note the items listed. 
• Select all the login items, then click the – symbol and restart your computer. 

If it runs fine, re-enable apps and services one at a time, restarting after each until the crashing returns. When the freezing starts again, you’ll know which application is the culprit.

Considering getting a new Mac? We can help you find the right model at the right price – see best MacBooks.

7. Reinstall your operating system

An in-place, or ‘soft,’ reinstall will reinstall Windows or macOS without affecting your data or applications. If the operating system is corrupted, this process will usually resolve the issue.

On Windows 10, try this:

1. Download the Windows 10 Media Creation tool, then run it and accept the terms and conditions.
2. Wait for the tool to prepare, then select ISO File.
3. Once downloaded, mount the ISO file by right-clicking and selecting Mount.
4. Run the setup.exe file to start Windows 10 Setup, then choose Next and accept the terms and conditions.
5. Ensure Keep personal files and apps is selected and choose Install.

Windows will now start the reinstall. After rebooting, you should be back at your desktop with updates installed.

Important note Official support for Windows 10 ended on 14 October 2025, and Microsoft no longers provides fixes, features and security updates unless you take action. For details, see our guide on 6 ways to prepare for Windows 10 losing security support.

On Windows 11, try this:

1. Download a Windows 11 ISO file, then mount it by right-clicking and selecting Mount.
2. Run the setup.exe file to start Windows 11 Setup and click Next on the Install page.
3. Accept the terms and conditions and ensure Keep personal files and apps is selected. Choose Install.

Windows will start the reinstall and, after rebooting, you should be back at your desktop with updates installed.

On macOS, try this:

1. Turn off your Mac, then press and hold the power button until you see Loading startup options.
2. Click Options > Continue.
3. Select Reinstall macOS > Continue.
4. Choose Macintosh HD > Continue.

8. Reset your computer

A reset will completely wipe your computer and place it back to factory settings with all settings, apps and data removed.

Typically, if the freezing still occurs after a reset, it’s likely to be a hardware fault or limitation. Ensure all data is backed up to either an external drive or cloud storage before resetting.

• On Windows 10, try this: Choose Settings > Update & Security > Recovery > Reset this PC > Remove everything > Cloud download.
• On Windows 11, try this: Choose Settings > System > Recovery > Reset this PC > Remove everything > Cloud download.
• On macOS, try this: Press the Apple Logo, then choose System Settings > General > Transfer or Reset on the right. Click Erase All Content and Settings and you’ll be prompted for your Admin password. Follow the on-screen steps.

9. Consider hardware limitations

Sometimes freezing isn’t caused by software, malware, or hardware faults – it might simply be your device’s hardware struggling to handle the task at hand. This is especially true for older machines with ageing CPUs, integrated graphics, low Ram or older mechanical hard drives (HDDs).

Check the minimum and recommended specs for the program or game you’re using (these are typically listed on the website). If your CPU, Ram or GPU falls below the recommendations, crashes are likely.

Join Which? Tech Support

Get tech confident for less

Solve your tech issues and get expert buying advice by chatting to our support team as often as you need. From only £4.99 a month.

Join Which? Tech Support

Cancel any time

Which? Tech Support can help you keep on top of your home tech. Our experts explain things clearly so that you can resolve issues and feel more confident using your devices.

Get unlimited 1-to-1 expert support:

• By phone Clear guidance in choosing, setting up, using and resolving issues with your home tech devices.
• By email Outline the issue and we’ll email you our answer.
• By remote fix We connect securely from our office to your home computer and resolve issues while you watch.
• In print Which? Tech Magazine, six issues a year delivered to your door.

You can join Which? Tech Support.