What is Microsoft Security Essentials?
Microsoft Security Essentials is free antimalware software for your computer. It helps protect against viruses, spyware, and other malicious software. It's available as a no-cost download for Windows 7, Windows Vista, and Windows XP SP2 and higher.
Microsoft Security Essentials is always kept up to date, runs quietly in the background, and schedules scans when your computer is most likely idle. You only see alerts when you need to take action.
Note: In Windows 8, Windows Defender replaces Microsoft Security Essentials. Windows Defender runs in the background and notifies you when you need to take specific action. However, you can use it anytime to scan for malware if your computer isn’t working properly or you clicked a suspicious link online or in an email message.
Learn more about Windows Defender
For more information, see Help protect your PC with Microsoft Security Essentials.