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Why is my computer so slow?

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While many people resign themselves to a life of waiting five minutes for their computer to load up, others spend hundreds on upgrading their PC or laptop every few years — we’re here to show you that neither of these is necessary.

In this guide, we outline the most common causes of a slow computer and lay out a step-by-step guide for solving each of them. Perform the simple fixes and tune-ups presented here — none of which take more than a few minutes — to get even the slowest of computers to running at their fastest again. 

Read on to find out all the most common causes of a slow computer and what you can do to solve them, including:

  • What makes a computer slow
  • How restarting your computer could be a simple fix for a lagging PC
  • How to reduce the number of programs that open when you start up your computer
  • How to uninstall the programs you no longer use to free up space on your hard drive
  • How to reorganise your hard drive
  • How to delete the temporary files that are clogging up your hard drive
  • How to set up your antivirus software so it protects your computer without slowing it down
  • How to tell if your computer is running slowly due to a virus
  • Why updating your software can speed up your computer
  • How changing web browser can make your PC or laptop run faster
  • How to disable resource-sapping browser extensions
  • How dusting your PC could make it run faster and stop it from freezing

What makes a computer slow?

Macbook on wooden floor

Your computer can slow down for a whole host of reasons, and what’s more, it may not be immediately apparent what in particular is affecting your PCs performance. The fastest way to get your computer back up to speed is to run through the list of the most common problems and perform the fix for each.

Think of this as like an MOT for your PC — once you’ve performed each of the simple bits of maintenance in this guide, your computer will be running its best again unless there’s a more serious issue that needs solving by a professional.

Here’s our rundown of the most common issues that cause home computers to slow down alongside a simple step-by-step guide to resolve the issue in minutes.

You need to restart your computer

How long does it take? A few minutes

While turning it off and back on again is a cliché when it comes to fixing a faltering computer, that’s for good reason — programs and files can still sap up your PC’s processing power long after you’ve closed them. If your PC becomes sluggish, your first step should be to save all of your files and restart your machine. This will flush out the system and give you a clean slate to work from, and may very well be all it takes to get your PC back up to speed. You should also get into the habit of shutting down your computer completely after each use rather than leaving it in sleep mode.

Too many programs are opening on start up

How long does it take? 5 minutes

One of the biggest issues people have with their home computer is that they take an age to start up. A lot of the time this is caused by too many programs being set to automatically start when your computer is switched on. Some software — such as antivirus programs — should be set to run as soon as you launch your computer, but most others should only open when you need them.

If your computer takes an age to start, this simple fix could be the end of your problems:

How to disable startup programs on Windows 8 and 10:

  • Hit the Windows key + X — this will reveal a small menu called the Quick Link menu above the Windows icon
  • Select ‘Task Manager’ from the Quick Link menu. This will open a new window.
  • Select the ‘Startup’ tab from the icons that run across the top of the Task Manager window. Right-click any programs that don’t need to be opened at startup and select ‘Disable’.

How to disable startup programs on Windows 7 and older:

  • Click the Start button, then search for ‘System Configuration’ in the search box and select the program of that name when it appears.
  • Click the ‘Startup’ tab from the menu along the top of the System Configuration window, and then untick any program you don’t want to be opened straight away.
  • A dialog box will appear telling you to restart your computer for these changes to take place. Save any important files you have open in the background and click ‘Restart’.

Stopping as many programs as possible from running as soon as you start up your computer could potentially end your slow startup times. Furthermore, it could also make your computer run faster beyond booting up, as you won’t have unneeded programs you didn’t know about running in the background.

Uninstall the programs you don’t use

Laptop on table beside coffee and a houseplant

How long does it take? 5 minutes

If there are any programs taking up space on your hard drive that you no longer use, you may be able to significantly speed up your computer in minutes by removing them.

Here’s how to uninstall programs you no longer use from your PC:

How to uninstall programs from Windows 8 and 10:

  • Hit the Windows key + X to reveal the Quick Link menu and select ‘Control Panel’.
  • Select ‘Uninstall a program’ under the ‘Programs’ heading.
  • Select the programs you want to remove from your computer and click the ‘Uninstall’ button. Some programs have their own uninstaller that boots up at this point — if this is the case, follow the instructions to complete their removal.

How to uninstall programs from Windows 7 and older:

  • Open the Start menu and then select ‘Control Panel’.
  • Select ‘Uninstall a program’ under the ‘Programs’ heading.
  • Select the programs you want to remove from your computer and click the ‘Uninstall’ button. Some programs may initiate their own uninstaller in a separate window at this point, and you should follow the instructions as they’re presented to remove them.

When you’re clearing your computer of unused programs, make sure to keep an eye out for unneeded software that came bundled with your computer and out-of-date versions of antivirus programs. Be sure to remove any games that your kids installed on your computer and no longer play, as these can take up several gigabytes of space.

You have too many programs or browser tabs open

How long does it take? A few minutes

A sure-fire way of slowing down your PC is running too many programs or opening too many browser tabs at once. Every computer has its limit, and once you ask your computer to run more software than it can handle, it will inevitably slow down or even freeze.

To prevent this from happening, you should make sure to close programs when you’re finished using them rather than minimising them, as they’ll still use up processing power if they’re left dormant in the background.

When browsing the internet, it can be easy to end up with dozens of open tabs. However, you should try to limit the number of tabs you open, favouriting the pages you want to come back to rather than leaving them open and continuing on to something else.

Your hard drive needs defragmenting

How long does it take? A few minutes to launch the program, which could take up to a few hours to run in the background

While this sounds complicated, it is basically a way or reorganising your hard drive — which becomes disorganised as you save, re-save, and delete files during everyday use — so it stores all of its information in the most efficient way possible.

Depending on how fragmented your hard drive is, the defragmentation process can take a few minutes up to several hours. The program, which only takes a minute to launch, runs in the background of your computer, so it won’t prevent you from performing other tasks while it’s running. Moreover, the longer the program takes to run its course, the more benefit you’re likely to see from it.

How to defragment your hard drive in Windows 8 and 10

Machines running on Windows 8 onwards automatically defragment themselves every week, as they come preprogramed to do so. Unless you’ve gone in and changed the default settings, you therefore shouldn’t need to perform a manual defrag.

However, if your computer is running particularly slowly, it can be worth checking in case your hard drive is fragmented. Here’s how to do so:

  • Hit the Windows key + Q to open the Windows Search function.
  • Search for ‘Defragment’ and select the ‘Defragment and optimize your drives’, which will open a separate window.
  • Check that the ‘Scheduled optimisation’ option at the bottom of the window is set to ‘On’, and the frequency is ‘Weekly’.
  • If any drives are indicated as being over 10% fragmented in the ‘Current status’ column, select it and click ‘Optimise’ to defragment the drive.

How to defragment the hard drive in Windows 7 and older

  • Click the Start button, then select ‘All Programs’ and then ‘Accessories’.
  • From this menu, select ‘System Tools’ and then ‘Disk Defragmenter’.
  • Enter your administrator password if prompted, and then hit the ‘Defragment Now’ button to begin the process. This may take several hours if your hard drive is particularly cluttered, but you can still use your computer for other tasks while this runs in the background.

You need to delete temporary files

Woman using laptop in a cafe

How long does it take? 5 minutes

Temporary files, which are a by-product of everyday computer use, accumulate on your computer and can start to slow it down after a while. Removing these files only takes a few minutes, but can potentially free up gigabytes of space on your hard drive and help speed up your PC. Here’s how to do it:

How to delete temporary files in Windows 8 and 10

  • Hit the Windows key + Q, search for ‘Disk Cleanup’, and then select ‘Free up disk space by deleting unnecessary files’.
  • Disk Cleanup will perform a scan of your files to calculate how much space you can save. This should take a few minutes.
  • Once the scan has been completed, you’ll be presented with a list of temporary files how much space you could save by getting rid of each. Select ‘Temporary files’, ‘Temporary internet files’, ‘Offline webpages’, ‘Download program files’, ‘Thumbnails’, and ‘Recycle bin’ and then click the ‘Ok’ button to delete these files.
  • Disk Cleanup will then remove these files from your computer. This could take up to a few hours, but you can still use your computer in the meantime.

How to delete temporary files in Windows 7 and older

  • Click the Start button and then search for ‘Disk Cleanup’ in the search box.
  • Select ‘Disk Cleanup’ from the list and wait for the scan to finish — this should take a few minutes.
  • Select ‘Temporary files’, ‘Temporary internet files’, ‘Offline webpages’, ‘Download program files’, ‘Thumbnails’, and ‘Recycle bin’ and then click the ‘Ok’ button to delete these files.
  • Disk Cleanup may take up to a few hours to complete this process — depending on how many files you’re deleting — but as the program runs in the background, you’ll still be able to use your computer while it runs.

Depending on how old your computer is, defragmenting its hard drive could free up several gigabytes of space and significantly improve its performance.

You don’t have the right antivirus program

While having a fully-functioning and up-to-date antivirus software installed on your computer at all times is essential for your security, the wrong bit of software — or the right bit of software that hasn’t been set up properly — can significantly slow down your machine.

If your antivirus automatically runs a resource-sapping full system scan every week, it can grind all but the most powerful computer to a halt for a few hours. If this is the case, you’re likely to cancel the scan each week, putting your computer at risk.

To get around this, go into your antivirus program’s settings and configure it to perform its weekly scan at night when you won’t be using your machine. If your antivirus software doesn’t allow you to schedule when you want it to perform a scan, we recommend an upgrade.  

You have a virus

If you have been skipping those antivirus scans or you’re only running a free piece of antivirus software, your slow computer speeds could be caused by a virus or malware. Make sure your antivirus program is up-to-date and then run a full system scan, which should detect and remove any malicious code that has been running in the background of your computer and slowing it down. If your computer was being affected by malware, this is likely to speed it up significantly. However, if you still think your PC may be infected, it’s important to seek the opinion of a professional.

Whether or not your PC’s poor performance was being caused by a virus, it’s important to follow basic internet security advice to ensure you aren’t infected with malware in the future. While there’s no need to be paranoid while browsing the web, there a few basic security tips that will help ensure your online security:

  • Don’t visit websites that seem suspect or your browser flags as having been infected with malware.
  • Don’t open any files attached to emails from an address you don’t recognise and trust.
  • Don’t download any files from websites you don’t trust.
  • Ignore all emails that seem suspect, especially if they’ve been sent from a “Nigerian prince”.

Stick to these rules of thumb and you’re unlikely to ever be infected by malware.

Your software isn’t up to date

Woman using a laptop beside glasses

How long does it take? A few minutes

While it can be tempting to ignore them, when a piece of software alerts you about a new update with a pop-up, you should perform it as soon it’s convenient. Web browsers, programs, drivers for external devices such as printers, and Windows itself release regular updates to fix any glitches and security flaws. Ignoring the prompts to perform these updates can not only slow your computer down, but also make it vulnerable to the latest malware and viruses.

These updates rarely take more than a few minutes to run, so make sure to keep on top of them to keep your computer running as fast and as securely as possible.

You’re not using the right browser

If you’re running a windows PC, it will have come with Internet Explorer as the default web browser. You can instantly speed up your computer by downloading either Google Chrome or Mozilla Firefox and setting it as your default browser instead, as these two programmes are much more efficient.

Make sure you don’t delete Internet Explorer from your computer altogether after you replace it, however, as Windows still requires it to perform some essential functions.

You have too many extensions on your browser

How long does it take? A few minutes

If your computer is particularly slow when you’re using the internet, it may be the case that a browser add-on or plugin is draining up resource and slowing your machine down. This is often the case with add-ons or search bars that come bundled with antivirus software.

If you find your computer is particularly slow when you’re on the internet, remove browser extensions and toolbars you don’t need. This is how:

How to disable extensions on Mozilla Firefox:

  • Hit the ‘Menu’ button in the top-right corner of the browser
  • Select ‘Add-ons’, then ‘Extensions’, then disable or remove each unwanted item from the list

How to disable extensions on Google Chrome:

  • Click the menu icon (which looks like three small squares stack on top of one another) in the top-right corner of the browser.
  • Select ‘More tools’ from the drop-down menu, then click ‘Extensions’.
  • Untick or bin any unwanted extensions in the list.

How to disable extensions on Internet Explorer:

  • Click the ‘Tools’ button (represented by an illustration of a cog) in the top-right corner of the browser, then select ‘Manage add-ons’.
  • Under the ‘Show’ tab, select ‘All add-ons’, choose all of the unwanted add-ons you want to disable, the click the ‘Disable’ button.

Your computer needs dusting

How long does it take? A few minutes

If you’ve tried all of the above fixes and your computer is still running slowly, you may find that your problem is actually external. If your PC is coated in a layer of dust, its internal components may not be receiving adequate ventilation, slowing the machine down and increasing the likelihood of a crash. A thorough dusting might be all it takes to dramatically increase its speeds.

If you own a laptop, make sure you aren’t blocking its vents, which are usually found on its sides, when you use it — this can often happen if you place your laptop on a pillow when you’re on it.

Your operating system’s animations are slowing your computer down

Pair of glasses on a Macbook

How long does it take? A few minutes

The visual effects of your operating system — such as the smooth transitions that happen when you close and minimise a window — can make the experience of using your computer slick and enjoyable, but if your PC’s hardware isn’t up to scratch, they can seriously slow down its performance.

Disabling your operating system’s animations is therefore a great way of speeding up an old or underpowered computer. Here’s how to do it:

How to disable visual effects on Windows 8 and 10:

  • Hit the Windows key + X, then select ‘System’ from the menu that appears above the Start button. A new window will open.
  • Select ‘Advanced system settings’ from the list of options in the top left-hand corner of the System window. A smaller window will open titled ‘System properties’.
  • Under the ‘Performance’ heading, hit the ‘Settings…’ button, then tick the box for ‘Adjust for best performance’ and hit ‘Apply’. This will remove all unnecessary animations and free up your computer’s resources for other tasks.

How to disable visual effects on Windows 7 and older:

  • Hit the Start button then select ‘Control panel’.
  • Choose ‘’Performance information and Tools’ from the menu, then ‘Adjust visual effects’.
  • Tick the box for ‘Adjust for best performance’ and then hit ‘Apply’.


So, there you have it — our breakdown of all of the most common causes of a slow computer and a quick and easy fix for each. Perform these bits of maintenance on your PC or laptop and you’re sure to improve its speeds unless there’s a more serious problem that a professional will need to fix.

You can also ensure your computers and laptops are always performing at their best by signing up with LetUsFixIT today. By doing so, your computer will be automatically protected and enhanced by our PC tune-up software, which diagnoses and fixes over 180 issues that cause a slow computer. You’ll also have access to your own personal tech support team through our one-click live chat support, through which we’ll be able to talk you through all of these quick fixes for a slow computer step-by-step.