When you open a file in Windows, such as an .exe, .cmd, .reg, .regedit, .secfile, .com, or .bat file, a different program or file may start. Additionally, the icon for the file may not appear as expected.

Use this tool to find and remove specific prevalent threats and reverse the changes that they made (see Covered malware families). For comprehensive malware detection and removal, consider using Windows Defender Offline or Microsoft Safety Scanner.

When critical Windows system files are missing or corrupted, your operating system may begin to malfunction. Common symptoms include Windows features not working properly, system errors, or Windows becoming unresponsive or freezing.

Real-time protection is a feature in the Windows Security app that continuously monitors your device for potential threats such as viruses, malware, and spyware. This feature ensures that your device is actively protected by scanning files and programs as they are accessed or executed.

Get security info and tips about threat prevention, detection, and troubleshooting. Including tech support scams, phishing, and malware.

One of the most common ways of transmitting computer viruses is through file attachments. To help protect you and your recipients against computer viruses, Outlook blocks the sending and receiving of certain types of files (such as .exe and certain database files) as attachments.

Provides Windows client guidance for IT Pros to protect against speculative execution side-channel vulnerabilities.

Learn about the Windows Security app and some of the most common tools you can use.

If you can’t install, uninstall, or update a desktop program in Windows 10, the Program Install and Uninstall troubleshooter can automatically fix common issues such as corrupted registry keys or incomplete uninstall data.

Last Updated: March 27, 2026 ISSUE Starting around March 12, 2026, classic Outlook might crash and then prompt to start in Safe Mode. This issue is happening when older builds of classic Outlook are using the newest version of the Teams Meeting Add-In build 1.26.02603. For example, this issue happens on Current Channel if the classic Outlook build is equal or lower than Version 2402 (Build ...