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 if you clicked a suspicious link online or in an email message.
To scan your computer with Windows Defender:
Tap or click the Search charm, search for defender, and then open Windows Defender.
On the Home tab, click a scan option, and then tap or click Scan now.
You can't use Microsoft Security Essentials with Windows 8 or Windows RT, but you don't need to. If you install two different kinds of antivirus software, they might conflict. If you want to use antivirus software from another provider, uninstall Windows Defender first.
Some malicious software will not allow you to access Windows Defender or other antivirus software. To help detect and remove the malware, you can start your computer by using a Windows Defender Offline CD, DVD, or USB flash drive. Learn more.
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