Microsoft acknowledged the growing threat of spyware with the launch of Windows Defender a few years ago. It’s available for Windows XP through to Windows 7. In Windows 8, which is the most secure version of the OS so far, Microsoft provided an enhanced version of Defender which also protects against malware – effectively rolling Security Essentials (Microsoft’s free antivirus program) and Defender into one.

This rubbed all the security software companies up the wrong way, so Microsoft provided an option to turn off Defender when a trial version of a security suite was installed on a new PC or laptop – it’s bad practice to run more than one antimalware engine at the same time. They will probably conflict with each other and cause severe performance problems.

However, should you decide not to activate that McAfee or Norton trial, Defender won’t automatically enable itself again, so you’re left unprotected from the viruses, Trojans and other nasties that could play havoc with your system, and even leave you out of pocket.

It’s easy enough to check if Defender is running: simply look for its icon in the Notification area (the space to the left of the clock to the right of the Taskbar). It might be in the list of hidden icons, so click the little upward-pointing arrow and look for a castle icon.

Don’t worry if you can’t find it – it may still be running, or your computer might already be running other security software which is doing a similar job. However, if you’re still not sure or you know your computer definitely doesn’t have an antivirus program or security suite, here’s how to enable Windows Defender.

Step 1: In the Start menu (or on Windows 8’s start screen) type Defender. Windows Defender should appear in the list. Click on it to launch the program. If it’s already running, and you see the main window, skip to step 5.

Windows Defender search

Step 2: You might see a message like the one below, showing that Defender is turned off and isn’t protecting your computer. If so, search for Action Center in the Start menu (or screen if using Windows 8) and run that.

Windows Defender turned off

Step 3: In Action Center, click on the Security tab to check which program is handling spyware and unwanted software protection. If you want to enable Defender in place of another suite such as McAfee, you should use the Control Panel to uninstall that first.

Windows 8 Action Center

Step 4: When that’s done, type Defender again in the Start menu and, if it’s turned off, you’ll see a message and a link to turn it on. Click it to turn on Windows Defender.

Windows Defender click here to turn on

Step 5: Assuming your computer isn’t protected, the Windows Defender main window will open on the desktop. Chances are, the spyware definitions will be out of date, so now’s the time to update them. Click the Check for Updates button.

Windows Defender (Win 7) update

Step 6: When that’s done, you should see a nice green bar showing that Defender is up to date and protecting your computer.

Windows Defender up to date

Step 7: Click the Tools link at the top, and then on Real-time protection in the left pane. Check that it’s enabled and then choose options for scanning downloads, attachments and programs that run on the computer. We advise enabling all the options here.

Windows Defender real-time protection

As mentioned at the beginning, in versions of Windows prior to 8, Windows Defender does not scan for viruses, so ensure that your computer has some antivirus software installed. If not, there are many to choose between, including free and paid-for versions. Check our antivirus software reviews for recommendations.

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