How to Troubleshoot Your Slow PC

Speeding up a slow PC can be a challenge, particularly when dealing with older hardware that may be on the cusp of needing an upgrade or replacement anyway. Sometimes, a system simply needs a fresh OS install or driver update to perform significantly better. In other cases, upgrade or wholesale replacement are necessary.

This article is designed to help you troubleshoot a slow machine. Specifically, it walks through the process of determining whether your problem is more likely to be caused by software, hardware, or simply the age of the machine.

Initial Questions

Whether you are doing this for someone else or for yourself, here are a few “big picture” questions to consider:

Has the system’s performance changed recently? If the answer to this is “Yes,” did it change when you installed a specific application or OS update?
Has the entire PC slowed down, or just specific applications? If the problem is isolated to one app or a specific group of apps, have those applications been recently updated or modified?
Does the machine feel sluggish and slow to respond to feedback like typing? Does it have this problem in all cases, or only when certain programs are running? Does it have the same lag if booted in Safe Mode?
Does the system begin to run slowly after a few minutes of work or gaming, or is it slow from boot?
Is the system just slow, or is it also unstable? If it crashes, is there a specific application or application(s) that makes this happen reliably?

The answers to these questions will help you understand where the problem is likely to be. If the machine is smooth and responsive in Safe Mode but lags badly when booted to a normal desktop, check and see what applications automatically start when you boot up Windows 10.

The answers to these questions are as important as the baseline specs of the system, especially if you’re trying to save money.

How Do I Tell If My PC Is “Just” Slow?

A PC that’s “just slow” shouldn’t have any other real problems apart from the lack of performance. You should have a feel for how long it’ll take to open a webpage or launch a game, and you shouldn’t see any unexplained variation in those times or particular instability when performing them. A slow PC may thrash the hard drive if you ask it to open too many browser tabs simultaneously, but there should be a reasonable and predictable (to you) relationship between how much work you are asking your PC to do and how quickly it can do it. A machine that’s “just” slow shouldn’t have problems with pop-ups or persistent trojan and malware infections, and it shouldn’t be unstable.

If you’re a gamer on an old gaming PC, said system should still run the same games you bought it to play back then (with allowances for OS compatibility or driver issues). If you could run BioShock Infinite at 60fps on your current computer in 2013 you should be capable of running it today. If BioShock Infinite (or any other old game or application) plays and runs perfectly, but newer software doesn’t, you may be looking at a situation where you need to upgrade as opposed to dealing with an underlying hardware or software problem.

Any PC still using a magnetic HDD is going to feel slower than a PC equipped with a SATA or M.2-based SSD. Any PC with less than 4GB of RAM is going to struggle at least some of the time under even moderate workloads. 8GB should be considered a minimum for any modern gaming. Dual-core CPUs without Hyper-Threading / SMT and CPUs based on Intel’s Pentium, Celeron, or Atom product lines are more likely to “feel” slow, even if the system is well-configured. Systems based on old AMD CPUs from the Phenom II era or the Bulldozer/Piledriver product families do not offer particularly high performance.

A system that was brand-new in 2013 and hasn’t been upgraded since shouldn’t feel like the latest-and-greatest in 2020 — but it shouldn’t be riddled with unexplained performance drops, either.

Tracking Down Software Problems

Performance problems are more likely to be software-related if they are associated with an underlying change to the OS or target application. If you’ve been gaming with no problems but recently bought your first new title in months, your GPU drivers may need to be updated to play it appropriately. It’s never a bad idea to check the minimum specifications for a new title to make sure you meet them: If you’ve got a GTX 480 and the game recommends a GTX 770 as a minimum card, you may well have found the cause of your problem.

Similarly, if you have an older system and you are having issues related to a specific subsystem (networking, sound, video), it may be worth updating your chipset and component drivers as well. The chance of this solving a problem is much higher if there’s an actual identified issue with what you’re using already, but I’ve had reinstalls clear up issues before from seemingly unrelated causes. It’s rare, but the chance isn’t zero.

Tools like Task Manager can sometimes be used to troubleshoot basic software problems with responsiveness and performance. Consistently high CPU usage may indicate a problem with an application, especially if it’s a browser and especially if killing the process improves system responsiveness. Some browser extensions can cause higher CPU usage under certain circumstances.

When you check Task Manager for CPU usage, you can also check the Startup tab. Make sure you recognize the applications that are loaded and running. You may not recognize every process listed in the “Processes” tab, but look for suspicious names or random, nonsense strings of text. In some cases, this may be a sign you’ve been infected by malware — and malware can steal CPU and GPU time for cryptocurrency mining and harm overall perf.

Event Viewer may contain data related to a performance issue or slowdown, but honestly, it’s a crapshoot and interpreting Event Viewer isn’t all that easy for the common user. I’m not touching on it much here as a result.

If you are concerned that old 3D drivers might be hanging around on your rig and cluttering up its performance, tools like Display Driver Uninstaller can be used to completely remove these traces. I use DDU for reviews when testing AMD and Nvidia cards. Booting into Safe Mode, running the tool, and then booting back to Desktop adds some steps compared with just installing a newer driver. But if you’re trying to troubleshoot performance issues, DDU is a good way to ensure you’ve cleansed your metaphorical palate. If you are having issues with your sound card or network solution, it may be worth visiting your motherboard vendor to see if they’ve released updated drivers for these components, for example.

When all else fails, a full Windows reinstallation will almost always nuke any software-related problems and let you determine if a hardware upgrade is necessary. I try very hard not to take this step for obvious reasons — “Just reinstall Windows” is the kind of advice that cost US citizens millions when deployed as part of a scheme to lie to people about the state of their software. Most people do not want to go to the hassle of reinstalling Windows and losing their current data installations in the process. But if you are facing weird performance issues that you can’t lock down any other way, and you’ve tried the other steps discussed here, it’s one way to deal with the problem.

There is an exception to this. Sometimes, a Windows Update is responsible for changes to user systems that cause high CPU usage or break Start Menu functionality. Upgrading components or an entire PC is no guard against these sorts of failures. In these instances, even a full Windows reinstall may not fix the issue.

We’ve discussed the software side of the equation. Let’s talk about what which hardware issues are most likely to slow a PC. I’ve tossed in a fair bit of discussion about what component failure looks like in each case to illustrate the difference between the problems that sap performance and the problems that turn your computer into an expensive paperweight.

Hardware Failure Characteristics (and Which Ones Hurt Performance)

RAM: Failing RAM can make a game run more slowly, but only if the CPU is still having some luck pulling data out of it at all. More commonly, applications just crash. The distinguishing characteristic of RAM failure is that there isn’t automatically a distinguishing characteristic. If the failure has occurred at a high memory address, you may only see the issue intermittently when you have a lot of programs loaded. It may happen mostly in games if games are what you typically run, but a RAM failure will pop up anywhere given enough time. Applications like MemTest86+ can be used to test RAM. MemTest86+ is the only RAM test I recommend — I’m not saying it’s the only good application available, but I’ve seen other RAM testers claim that memory was good when it actually wasn’t. I’ve never seen MemTest86+ throw a false positive or false negative.

GPU: A failing GPU may display odd colors and textures whenever you run a 3D application, or function perfectly for basic desktop work but fail if asked to render a video or play a 3D game. Using a third-party utility like MSI Afterburner may allow you to resolve the issue by either lowering the GPU/RAM clock or increasing the chip’s voltage, but these fixes tend to be temporary. Games may crash at load or may run for short periods of time. The problem may begin in a specific title, but it probably won’t stay isolated. A failing GPU may also refuse to install its own driver.

A GPU that runs perfectly for a long period of time before you start seeing errors or texture flickering may be overheating, but may not be damaged yet. Dust the system and see if that improves things. Many games offer benchmark modes for testing GPUs, and running these tests in a loop will often produce a failure, though it may take multiple loops through the test to see it happen.

GPU failures typically will not slow down the system, unless lowering the clocks yourself (temporarily) fixes the problem.

CPUs: CPU failures are difficult to categorize because CPUs almost never fail. If your CPU’s performance is dropping, chances are it’s a thermal issue — either a mismounted heatsink or a thick build-up of dust. Make certain that your heatsink is properly mounted with an appropriate amount of TIM (thermal interface material) between the CPU and its heatsink.

Power Supply: One way to discover your PC PSU needs replacement is for it to burst into flames without warning. (Ask me how I know!) A far less terrifying method is for your machine to simply flip off or reboot during a gaming session or rendering run. In some cases, your motherboard may warn you that power delivery from the PSU was disrupted. Power supply failures can superficially resemble RAM failures, but MemTest86+ won’t return errors and the PSU won’t trip while running basic desktop tasks unless it’s truly having issues. In these cases, your motherboard may also report that one or more of the power rails is low. Bad PSUs often don’t cause slowdowns; they cause shutdowns.

Hard Drives: Mechanical spinning drives may click quietly and repeatedly when attempting to access certain parts of the drive, or I/O performance may drop badly when attempting to access data. Event Viewer may also log hardware failures if the OS can’t read data across the bus properly. SSDs will not click (no moving parts), but they may display the same longer-than-expected access times or sharply reduced performance as the CPU tries to read data from damaged parts of the drive. In many cases, these types of failures will kill the drive altogether rather than leaving it limping along at a lower level of performance.

Low Storage Space: Not a “failure” as such, but it’s a hardware issue, not a software one. Windows generally does not like to run without hard drive space. The less free space you have, the less the OS likes it. This can lead to errors, application crashes, and cache thrashing, all of which harm performance.

Heat: I’ve decided to list “heat” as a common characteristic of hardware instability and lost perf, rather than breaking this out by CPU and GPU. Dust is an amazing insulator. Pack in enough of it and fans won’t even spin. I’ve lost count of how many gamers and readers I’ve met who were afraid they needed to buy new hardware, only to discover that dusting what they owned restored the performance they were missing. Laptops can be a little trickier to dust than PCs, but if you have a desktop and are experiencing instability while gaming, pop the side of your case off and see if things don’t improve. It’s no guarantee — but it’s not a hard thing to test, either.

A PC with issues in just one game or a handful of games may only need a driver update, especially if the titles are newer. A machine that never crashes during desktop or browser work but slows down and crashes during gaming may need to be dusted. When I run into people who are suffering PC crashes while gaming, one of my first pieces of advice is to take the side panel off their computer. The growing popularity of laptops for gaming has made this fix a little less applicable than it used to be, but you’d be amazed how many “unstable” PCs become stable if you just improve airflow. Dusting is obviously the best way to do this, but you can’t always take time from a raid instance or Fortnite game to hunt down a can of compressed air. Just taking a side panel off is a quick way to test this theory.

Systems are less likely to crash outright from high temperatures than they used to be, but throttling can still play merry hell with game performance. I always check thermals when I’m evaluating system behavior.

Of all the issues here, I’d say dust, driver updates, and low disk space are the three most common factors likely to cause slower-than-desired performance in the absence of hardware failure. Broken software can absolutely cause all manner of problems, but these cases tend to be specific and particular to the user in question (or the hardware in question) and are much harder to resolve in a general-purpose guide like this.

Questions? Tricky cases? Got a machine with an issue you can’t seem to fix? Drop it below.

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How to Troubleshoot Your Slow PC

Initial Questions

How Do I Tell If My PC Is “Just” Slow?

Tracking Down Software Problems

Hardware Failure Characteristics (and Which Ones Hurt Performance)

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