If your computer is running Windows 8, you can use the built-in Windows Defender to help you get rid of viruses, spyware, or other malware.
If your computer is running Windows 7, Windows Vista, or Windows XP, Windows Defender only removes spyware. To get rid of viruses and other malware, including spyware, on Windows 7, Windows Vista, and Windows XP, you can download Microsoft Security Essentials for free.
In Windows 8, Windows Defender replaces Microsoft Security Essentials.
You can’t use Microsoft Security Essentials with Windows 8 or Windows RT, but you don’t need to because Windows Defender already provides built-in protection.