Windows Defender and Microsoft Security Essentials help protect your PC from malware and other threats in exactly the same way. You can't use Microsoft Security Essentials with Windows 8 and later, and you can't use Windows Defender with Windows 7 and earlier.
Windows Defender works on Windows 8 and Windows 8.1. It's built into Windows and ready to work as soon as you turn your PC on.
Microsoft Security Essentials works on Windows 7, Windows Vista, and Windows XP. You can download it from the Microsoft Security Essentials website.
Before the release of Windows 8, Windows Defender referred to a separate tool that focused only on antispyware. This tool is no longer supported, as it is now fully integrated into Microsoft Security Essentials and Windows Defender.
You can find out more about using our products on our security software help page.
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