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When to trust a website
Learn how to decide whether a website is secure and trusted before you download software or do business online.
Security checklist for Windows
Help make your PC more secure by using features like Windows Defender, installing important updates, and backing up your files.
Turn Windows Firewall on or off - Microsoft Windows Help
Enable or disable Windows Firewall.
I can't install Microsoft Security Essentials
Learn the different steps you can take when you are having problems installing Microsoft Security Essentials on your computer.
How do I remove a computer virus? - Microsoft Windows Help
Learn about antivirus programs, online scanners, and tools that help remove malicious software from your computer.