If some Windows functions aren't working or Windows crashes, use the System File Checker to scan Windows and restore your files. Though the steps below might look complicated at first glance, just follow them in order, step-by-step, and we’ll try to get you back on track.

Create a system restore point. In the search box on the taskbar, type Create a restore point, and select it from the list of results. On the System Protection tab in System Properties, select Create.

Turn Windows Security on or off. When you get a new device and start up Windows 10 for the first time, the antivirus protection that comes installed with the device is your default security app. However, Windows Security is pre-installed and ready for you to use at any time.

Follow these steps to automatically diagnose and repair Windows security problems by turning on UAC, DEP protection, Windows Firewall, and other Windows security options and features. Select the Download button on this page.

If you trust a file, file type, folder, or a process that Windows Security has detected as malicious, you can stop Windows Security from alerting you or blocking the program by adding the file to the exclusions list.

Learn how to remove malware from your PC. Use Microsoft Defender Antivirus in Windows 10 or Windows 11 to scan your PC for malware, viruses, or other threats.

Windows Security has reputation-based protection that can help protect your PC from potentially unwanted applications. Potentially unwanted app blocking was first introduced in the Windows 10 May 2020 update and is turned off by default for enterprise and consumer customers.

Virus & threat protection in Windows Security helps you scan for threats on your device. You can also run different types of scans, see the results of your previous virus and threat scans, and get the latest protection offered by Microsoft Defender Antivirus. Under Current threats you can:

Windows Security provides built-in security options to help protect your device from malicious software attacks. To access the features described below, tap the Windows Start button, type windows security, select it from the results, and then select Device security.

Windows Security is your home to manage the tools that protect your device and your data: Virus & threat protection - Monitor threats to your device, run scans, and get updates to help detect the latest threats. (Some of these options are unavailable if you're running Windows 10 in S mode.)