Sometimes your Windows 10 PC slows to a crawl, perhaps accompanied by a whirring fan and programs that barely respond. Often the problem is an application that is using a large share of the CPU’s power, leaving little left for other programs. Here’s how to check—and what to do about it.

The best tool to diagnose a Windows program that might be using too much system resources is a built-in utility called Task Manager.

RELATED: Windows Task Manager: The Complete Guide

To open Task Manager, right-click the taskbar. In the menu that pops up, select “Task Manager.” (You can also press Ctrl+Alt+Delete and select “Task Manager” from the list.)

If you see the simple Task Manager interface, click “More Details” at the bottom of the window.

In the full Task Manager window, click the “Processes” tab. You will see a readout of all the active processes and the resources they’re using. Processes are any applications or programs running on your computer, including vital system functions that run silently in the background.

To sort the processes by which one is using the most CPU, click the header of the “CPU” column. The process using the largest percentage of the CPU will appear at the top of the list.

At this point, if the CPU-hogging process is an application, you can attempt to close it using the usual methods (such as selecting File > Exit in the application’s menu or right-clicking the application in the taskbar and selecting “Close Window”).

If the application doesn’t respond, you can either wait for a task to complete (if you know that the application is actively working and not just hung), or you can force it to close. To do that, select the application or process name in the Task manager processes list, and click “End Task.”

After that, the process will close. If your machine suddenly becomes responsive again, then you know that the CPU-hogging application was the issue.

If the process hogging the CPU is a system process or a process that you don’t recognize, you could also try to reboot your PC. Immediately afterward, it might be wise to run a virus scan with Windows Defender just in case malware is causing the problem.

RELATED: How to Scan with Microsoft Defender Antivirus on Windows 10

If rebooting doesn’t fix the problem, you can also try updating the application or updating Windows itself. That may fix a bug in the software that is causing the process to hang. Good luck!

Profile Photo for Benj Edwards Benj Edwards
Benj Edwards is a former Associate Editor for How-To Geek. Now, he is an AI and Machine Learning Reporter for Ars Technica. For over 15 years, he has written about technology and tech history for sites such as The Atlantic, Fast Company, PCMag, PCWorld, Macworld, Ars Technica, and Wired. In 2005, he created Vintage Computing and Gaming, a blog devoted to tech history. He also created The Culture of Tech podcast and regularly contributes to the Retronauts retrogaming podcast.
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