Few things are more frustrating than a slow computer.
You turn the computer on and wait for the operating system to load.
You used the computer yesterday without any problems, and now, all of a sudden, it is slow?
This experience, although not uncommon, is a sign something is wrong, and usually occurs for specific reasons.
Here are the 10 most common.
Why Is My Computer So Slow All of a Sudden? (10 Potential Reasons)
1. Your Computer Might Have A Virus
Viruses come in many flavors, but a lot of them can bring your PC to a crawl.
Some forms of malware (unwanted malicious software) attempt to remain undetected and use as few system resources as possible.
Others will render your computer unusable until the virus is completely removed.
However, even the leanest of viruses leave some sort of footprint on performance.
Some telltale signs of malware are frequent, unexplained pop-up windows, browser redirects when surfing the web, and changes in system settings that you didn’t make.
If your computer is running slow all of a sudden and you suspect a virus might be the culprit, open the performance monitor for a glimpse at what’s consuming so many system resources.
To get there, run the Task Manager by pressing shift + ctrl + esc on the keyboard and then clicking on the “Performance” tab.
Usually (but not always), either insufficient memory or slow disk drives are the primary bottlenecks when it comes to your PC’s performance, so check these first.
Performance Monitor will give you a quick glance at which hardware is causing issues, but you can give even more detailed information in Resource Monitor.
To open the application, click on “Open Resource Monitor” at the bottom of the “Performance” tab.
In Resource Monitor, you can get more detailed information about which processes are consuming all of your RAM, CPU, and disk usage among other things.
If you see any particular process using a large number of resources, you might have found the culprit.
If you don’t recognize it, a quick Google search for the process name should tell you whether or not the software is legitimate.
If you suspect you might have a virus, use a good antivirus software, and scan your computer for unwanted software.
After the scan, we also recommend using Malwarebytes as it nicely complements AV software in finding and eliminating malware.
Some of the nastier viruses require a complete format and reinstallation of the Operating System, so be prepared for that possibility.
2. Low Disk Space
How much free disk space do you have?
If your hard drive is full or close to full, you might notice your computer running slowly in addition to other erratic behaviors including freezing or crashing.
A full hard drive can cause problems for the operating system for a couple of reasons.
First, the OS uses a piece of hard drive space for virtual RAM, known as a swap file or page file.
In order to free up memory for more immediate use, the OS will temporarily offload RAM contents to the hard drive to be retrieved and reloaded into memory when needed.
Your computer can reserve hard drive space for this purpose, but the swap file grows or shrinks depending on how much is needed.
If insufficient space limits the size of the swap file, your computer won’t be able to utilize RAM in the most efficient manner.
In addition, a full hard drive is a less efficient one.
It takes longer to index and reference files, and the hard drive can become more fragmented as well since there’s not enough free space to move the existing files around.
With the prevalence of solid state drives, this is less of an issue, but each millisecond lost can add up.
If your computer is low on storage, work on deleting or offloading unnecessary files.
Make sure you empty the recycle bin and your downloads folder, as these can be repositories for a slew of data if you don’t regularly clean them out.
If you’ve cleared out all of the obvious files and still come up against your storage limit, you can try Windows 11’s built-in tool called Storage Sense.
With this tool, you can clean up temp files and other directories.
Another tool we like is called CCleaner by Piriform.
3. Corrupt Operating System
A corrupt operating system can cause your PC to run slowly without warning.
What leads to a corrupt OS?
A whole host of causes like bad updates and improper drivers can lead to OS corruption, but one of the most common sources of the problem is an improper shutdown.
If you force the computer to shut down when it’s accessing system files, your risk of operating system problems is high.
Broken OSes often manifest themselves in the infamous blue screen of death (for Windows), but other issues are possible, too.
Your computer could take a long time to boot or might not even boot at all.
Even if the computer does boot properly, there might be underlying issues that won’t rear their heads until you try to access certain programs or perform a specific task.
If you suspect this might be the case, there are a few things you can try.
First, open up a command prompt in Windows.
Click on the Start button, and in the search field, start typing “command prompt” until you see the program appear in the search results.
Right-click on the program and choose “Run as administrator.”
When the prompt opens, type the following command and then press the “Enter” key:
DISM.exe /Online /Cleanup-image /Restorehealth
DISM stands for Deployment Image Servicing and Management, and the “online” switch uses files from Windows Update to download necessary files to fix corrupt files.
When the first command is done, next we will use the System File Checker (SFC) to scan for and repair the corruption:
Be patient as these two commands could take some time, especially if your system is already running slowly.
4. Your Hard Drive Is Failing
One of the most common causes of a slow PC is a failing hard drive.
This is especially true if your primary hard drive is mechanical, but even solid state drives eventually fail.
Sometimes a bad hard drive is difficult to diagnose because problems can be intermittent or sporadic, especially if only certain sectors have failed but the rest of the drive is intact.
I’ve seen some systems boot up and run as expected only to hit a brick wall when the OS accesses a certain service or dll on a bad sector.
One way to check for errors is the aptly named Check Disk utility.
Open up the command prompt again and type in the following command:
chkdsk c: /r
If Windows is installed on a different volume, replace the “c” with the letter assigned to your Windows partition.
Because the disk is currently in use by the OS, Command Prompt will ask if you’d like to run Check Disk at the next boot.
Type “y” and press enter, and then reboot your computer.
Depending on the size of your hard drive, this process could take some time, so be patient.
The /r switch tells Check Disk to attempt to “repair” errors, but this usually consists of identifying bad sectors, coning them off so they don’t get used again, and (if possible) moving the existing data to good sectors of the drive.
Another way to check the drive for errors is by using diagnostic tools.
Many PC manufacturers include built-in dialogs that you can access pre-boot by pressing a hotkey on the keyboard.
Short of that, you can use third-party utilities that work both in and out of the operating system.
If diagnostics report problems with the drive, back up your data and replace the disk as soon as possible.
5. Too Many Background Services Running
Do you notice several programs all starting up when you log in to your computer?
If so, you might have too many background processes and services running.
Usually, these programs have a minimal impact on your OS, but they can add up as you install more applications over time.
Because the effects of this phenomenon are cumulative, if your computer is slow all of a sudden, it’s possible that a single program is causing the computer to run slowly.
The culprit can be a particularly resource-hungry application or a poorly written one.
If you suspect this might be the cause of your sudden slowness, consider what programs you have installed recently.
Uninstall them one at a time, starting with the most recent, and test after each installation to see if your computer returns to normal speed.
If you need these programs, your best bet is to ensure that they don’t auto-run on startup.
This will ensure that the software only runs when you need to use it, so it’s not consuming resources in the background.
To check startup programs, we’ll head to Task Manager as we did above, but this time click on the “Startup” tab.
Click on the “Status” column heading to sort the programs by whether or not they run automatically when you first log in.
Examine any that are set to “Enabled” and disable any that you don’t need to run automatically.
Computers generate quite a bit of heat.
An average CPU runs between 100°F and 150°F (38°C to 66°C), and other components like graphics processor units (GPUs) only add to the problem.
Therefore, if your PC isn’t properly dissipating the heat—whether actively or passively—your computer can slow down.
Some sophisticated chipsets can instruct components to slow down in overheating situations in order to avoid damage to the components.
If this is happening on your computer, you’ll definitely notice sluggish performance.
Since the CPU is usually the hottest component, we can look at processor temps to get a decent idea of the overall temperature inside the computer.
One great way to monitor CPU temps is using the free HWMonitor tool by CPUID.
Download and install the software, then run the application and locate your processor.
Click on the plus sign to expand the information, and you’ll see a section with temperatures.
Temps higher than 150°F could indicate problems, and you never want to see the CPU above 200°F.
A sudden onset of high temps could indicate a fan failure, that your vents are blocked or clogged, or perhaps insufficient thermal paste between your CPU and its heatsink.
Your best bet for resolving the issue is to use a can of compressed air to blow the dust and lint out of your system.
If you’re still experiencing high CPU temps, check your fans.
The free Speed Fan utility will help you monitor fan speeds, and you should also run diagnostics if your PC has them to ensure fans are working properly.
7. Other Hardware Issues
In addition to hard drive problems, other types of hardware failures can result in a sluggish computer.
This is especially true if issues are present with your RAM, CPU, GPU, or motherboard.
With RAM, one or more sticks might be faulty, causing issues when the computer attempts to address those sectors.
In addition to slow performance, you might experience blue screens, shutdowns, or sudden reboots.
Sometimes you’ll get some indication of the problem, but not always.
A good diagnostic for testing memory is Memtest86.
Don’t be fooled by the name, though.
In addition to x86 architecture, the software can also work with ARM chips as well.
Download the software and extract the zip files.
Inside, you’ll see an executable file that you can use to create a bootable USB drive.
You’ll need to boot your computer from this drive so that the utility can have full access to the memory.
Motherboard issues are harder to track down as they can manifest in ways similar to OS problems.
Try reinstalling your OS and watching for the problem to recur.
If you have a discrete GPU, you might try removing it from your computer, if possible, just to test if the problem goes away.
8. Network Issues
Does your computer run slowly only when trying to do something online?
The problem could be your network connection.
A slow Ethernet or Wi-Fi connection can make it seem like your entire PC is sluggish since almost everything we do on a computer these days relies on a link to the Internet.
To test, try and run some software on your computer that doesn’t rely on the Internet—something like a music player using mp3s stored on your hard drive, viewing and editing photos, or simply using a word processor to create a document.
Does your computer still run slowly?
If not, then your network connection might be a problem.
If so, it’s important to determine whether the problem is internal or external to your computer.
If possible, switch networks or move the computer to another location to test if the network connection improves.
You can visit speedtest.net to test your Internet connection before and after that change.
Anything less than a 25-Mbps download speed will probably feel slow.
If the problem is with your network, contact your Internet service provider or network administrator for help.
If the problem appears to be internal to your PC, the most likely culprit is an outdated, missing, or corrupt driver.
Visit your manufacturer’s website to find and download the most up-to-date network drivers.
(You might have to do this from another computer if your connection is especially hosed.)
It’s also worth mentioning that your Internet browser could be the culprit even if your network and drivers are just fine.
To test, try a different browser.
If you rely on Edge, download Chrome.
If you use Chrome, try Firefox.
If the problem is the browser, it’s possible you have a buggy extension or plug-in that’s causing the logjam.
9. Outdated Or Corrupt Drivers
In addition to bad network drivers, faulty or missing drivers for any hardware elements can cause your computer to run slowly.
The most likely culprits are chipset, hard drive and hard drive controllers, and graphics card drivers.
If you suspect a driver issue, first turn to Device Manager.
Open a run dialog box by holding down the Windows key and pressing the “R” key.
Then type devmgmt.msc and press “Enter.”
In Device Manager, look for devices with an exclamation point beside them.
The icon indicates a missing or malfunctioning driver.
Even if you don’t have any exclamation points, you might still have a driver problem as Windows may have installed a basic form of the driver, but the proper driver is not installed.
The best way to get drivers is straight from the manufacturer of your PC.
Visit the company’s support website and search for downloads for your model number.
If you built your PC yourself, try to narrow down which component needs an updated driver and visit the component maker’s website.
If you’re not sure which device has the problem, start with the chipset (motherboard) and then work through the rest of the devices.
10. Antivirus Scanning
Antivirus software is critical to keeping your PC free from digital disease, but AV software can also be resource hogs themselves, especially when it comes to scanning your computer.
In addition to real-time monitoring offered by most AV packages, all good security software also conducts scans of your hard drive and memory for suspicious files and activity.
However, scanning can cause your computer to crawl.
When you notice a slowdown, open Task Manager, and examine your disk usage.
Click on the “Disk” column in the “Processes” tab to see which programs are utilizing the disk.
If your AV is occupying the disk, then it’s likely scanning for malware.
Scanning is critical, so don’t discontinue routine scans.
Instead, adjust the scan schedule to a time when you’re not usually using the computer.
It’s easy to become frustrated when your computer starts running slowly out of the blue.
These issues have a knack for popping up at the worst possible times, but with a methodical examination of the symptoms, you’ll be able to identify and resolve the problem like a pro.