When you open Task Manager and see that your CPU or RAM is at 100%, it doesn't necessarily mean that your hardware is failing; it may just be that your computer is working at full speed because of something running in the background. Many times, an antivirus or services within the operating system itself are the culprits.

For example, the Antimalware Service Executable (the engine behind Windows Defender) can spike CPU and RAM usage while scanning in the background, especially after a recent update. That constant scanning can use up almost all of your available resources.

There are also other processes like Sys Main, formerly known as Super fetch, that try to speed up access to your applications by preloading data, and in some cases, can take up a substantial amount of CPU. Additionally, if you have more than one antivirus installed, conflicts can arise and increase system usage due to duplication of tasks.

Antivirus Problems

It's not that the antivirus is a villain, quite the opposite! Modern antivirus programs use a lot of memory, and for good reason: to be able to compare millions of malware signatures instantly, they need to load a lot of information into RAM and be able to access it quickly.

What if the antivirus starts consuming too many resources for no apparent reason? In many cases, disabling real-time protection for a moment, waiting for the memory to stabilize, and then re-enabling it can resolve the spike caused by a temporary glitch. In other cases” especially after an update”it may help to adjust the scan schedule or exclude the MsMpEng.exe (antivirus) process from Task Scheduler so that it doesn't run with higher priority than necessary.

What you can do to prevent your PC from slowing down

The good news is that most of these problems have easy solutions.

First, restart your PC. It seems rudimentary, but a simple restart can clean up temporary processes or hanging tasks. Then, Open Task Manager and see which processes are using the most CPU or RAM. If it's clear which ones you don't need, you can close them.

Another option is to limit the programs that start with Windows. Many install without you noticing and then run in the background all the time; disabling them from startup helps a lot.

Similarly, if you suspect your antivirus is the culprit, reschedule its scans to times when you're less active or add exclusions to the antivirus to reduce its impact.

If your system is still slow, check for services like Sys Main (formerly Super fetch) that may be bothering you; Temporarily disabling them can make a big difference.

Ultimately, if 100% usage persists and you can't pinpoint the process, it may be due to a faulty or outdated hardware driver. Some poorly optimized drivers—such as network, GPU, or storage drivers—can cause high system usage without you even realizing it. Updating or temporarily uninstalling them may be worthwhile.