The Helpdesk
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The Helpdesk

How to Diagnose a Slow Windows 10 Computer

Photo by Kelly Sikkema on Unsplash

“My computer has been acting slow” is the bane of any end-user support professional’s existence. It’s one of the most common complaints, but it’s also so non-specific that it’s often hard to diagnose — it’s a bit like going to a doctor and only telling them “I feel sick.” But it is possible to figure out why a computer’s performance seems to be dragging, as long as you take the time to figure out what the symptoms are. Here are the things I consider when investigating a performance issue.

It’s Almost Certainly Not a Virus

“My computer has been acting slow” is often followed up with “do I have a virus?” And it’s almost never a virus, or even “malware,” the broader term for bad stuff that sneaks onto your computer. While it’s technically possible that something like that is causing an issue, it’s more likely that you’ll have symptoms like ads, fake error messages, and other very obvious signs. General slowness is far more likely to be caused by something else.

Just Get an SSD

Before I get too far into this process, I think it’s worth noting that right now (August 2021) the answer to this question in many cases will be “upgrade to a solid state drive (SSD) if you don’t already have one.” SSDs are a type of hard drive that are drastically faster when booting the operating system and loading programs, and many people will perceive the entire computer as being faster just from making that one change.

If you’re not sure whether or not you have an SSD already, go to the Start Menu and type “Device Manager” in the search. In Device Manager, expand the section called Disk Drives. There you should see a brand and model number that you can search to find out what kind of drive you have.

SSDs are more expensive than older hard disk drives (HDD), but their cost has dropped low enough that it’s a good investment. As of this writing, a 512GB SSD is near $50, and a 1TB can be found for under $100. If you’re still using an HDD, upgrading to an SSD is a great place to start.

Reboot, Even if you Think You Don’t Need To

I know that “turn it off, then turn it back on” has become something of a running joke, but . . . really, turn it off and back on again. Programs get locked up sometimes. Processes don’t close when they should. Computers have lots of code doing all kinds of things, and all of that sometimes interacts in negative ways. A reboot will clear out many problems in one step, so it’s worth doing before you start diagnosing.

And once you do reboot, give the computer a few minutes after getting back to the desktop before you check to see if the problem persists. It’s normal for Windows to take a bit to “settle,” because after a boot, it has to load startup programs and background processes. You can’t tell for sure how well the computer is performing until that’s all done.

Reset/Refresh Your Browsers

A screenshot of the Chrome reset and clean up settings.

In today’s era, we do an awful lot in the web browser. A small problem with your browser, or with certain pages you’re visiting, can make it feel like your entire computer isn’t running right. Fortunately, a huge number of browser issues can be cleared out by using the reset/refresh options built into the browsers themselves. These resets will flip settings back to their original state, clear changes that your extensions may have messed with, and wipe site cookies and cache/data. I find that this takes care of more than 90% of the browser issues I encounter.

To do a reset/refresh, do a web search for the settings in your specific browser of choice. Here are the links to the Google Chrome and Mozilla Firefox reset instructions.

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Check the Hard Drive Storage

A screenshot of the Windows File Browser showing a partially full hard drive.

Generally speaking, having more stuff on your hard drive won’t slow down your computer. (But it’s a surprisingly common misconception that it does.) However, if your hard drive gets very full, as in up over 90%, it can definitely slow the machine to a crawl. This happens because Windows no longer has any extra space on the drive to work with when swapping files around, or creating temporary files. So if your hard drive is that full, you may be able to improve performance by clearing some space. See my guide on How To Clear Hard Drive Space on Windows 10 for more on how to do that.

See Which Programs are Hogging Resources

A screenshot of the Windows Task Manager.

So far, we’ve just been doing some essential tasks for clearing out the most common problems, but now it’s time for some more in-depth diagnosis using the Windows Task Manager. First, click the Start button, then type “Task Manager” in the search, and then click Task Manager in the results.
Tip: you can also just hit Ctrl+Shift+Esc to go right to it.

Task Manager has a few different tabs that are going to be useful for this, but to start, click on Performance. Under this tab, the main things to look at are the CPU and Memory sections, because those are hardware categories that impact performance the most. Don’t stress too much about how the CPU usage bounces around, or what percentage the memory usage is idling at.

Instead, the main thing to look for is if either the processor or memory is staying very high, north of 80% or so. Constant, high processor or memory usage could definitely be the source of a performance problem. But that doesn’t mean that you need to upgrade hardware — more often it means that some program is taking up too many resources. To find out, click over to the Processes tab.

The Processes tab shows you exactly what’s running on your system, and how much of the processor and memory it’s using. What makes it an especially good tool for this job is that you can click the CPU and Memory headings on the columns to sort the list from highest to lowest usage.

Click the Memory heading to sort from high to low, which will show a down arrow next to the percentage. Now let it sit, and watch the list as it refreshes each second. Mainly look at the top of the list, and see if any programs are using way more than anything else. Your browser will likely be at the top, and Google Chrome in particular is notorious for using lots of memory. That’s not necessarily a problem, as long as you have enough memory for it to work with.

The main thing is to keep an eye out for programs that are hanging out near the top of the list, but that you don’t really need to have open all the time. Most of us probably have a few programs running automatically that aren’t essential, and there’s no sense in letting them use resources constantly. Once you’re done looking at the memory usage, sort the list by CPU usage, and again look for things that are either using way more than any other process, or are not needed.

Handling Resource Intensive Programs

A screenshot of the Window Task Manager, with a context menu open for disabling a program.

If you’ve identified some programs that are using too many resources, you have a few options. One word of warning though: If you don’t know what something is, it’s better to not mess with it. Some of your computer hardware may have small utilities that run to help it function, and you likely want those to work as designed.

If it’s a program you don’t need at all, you can always uninstall it: click Start, search “Add or Remove Programs” and open that from the results, then select the program from the list and click the Uninstall button.

If it’s a program you do need, but it’s running when you don’t need it, you can prevent it from running at startup easily enough. Back in the Task Manager window, click the Startup tab. You’ll see a list of all the programs that are loading in the background when you log into windows. For any that you don’t want running constantly, right-click the name on the list, then choose “Disable” from the menu.

Check for Malware

Another potential software problem is malware, the catch-all term for anything bad that winds up installed on your computer. For that, a reformat and reinstall of Windows is ideal, but it’s often worth trying a malware scanner. I’ve mostly used Malwarebytes in the past, but search for articles from reputable tech sites about the best current scanners.

If None of that Works

If your computer’s general performance is still slow, you’re down to look at either a major issue with Windows, or a problem with the hardware. If the problem is Windows, a wipe of the hard drive and a fresh install might solve the problem. If it’s hardware, you’d need to run diagnostics, or test by swapping out parts. The two parts most prone to failure are memory and hard drives. For issues with general slowness, the hard drive is the most likely culprit.


Sometimes a slow computer needs to be replaced, and sometimes it needs a hardware upgrade. But in many cases, the performance is just suffering from one issue or another that isn’t too hard to solve on your own. With these steps, you’ve got a pretty good start on sorting out the most common issues.

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Sam Cook

Sam Cook


Former writer for and, currently a technology professional, teacher, and father. I write about whatever is on my mind.