Attention, Windows XP, and Vista users: Microsoft Security Essentials turns itself off as your operating systems are not supported anymore. Please see some free third-party tools, such as Avast Free Antivirus, BitDefender Free, or AVG.
Microsoft's own free anti-virus software - Microsoft Security Essentials - is easily understandable and does not require much configuration. This is a replacement for Windows Defender in Windows Vista and 7, adding anti-virus and network protection functionality.
Microsoft Security Essentials is available for Windows 7, for 32-bit and 64-bit editions.
Windows XP and Vista users cannot install Security Essentials anymore, and existing users will see red popups about the end of support.
Because Microsoft Security Essentials replaces the traditional Windows Defender in Windows 7, the latter is not allowed to start anymore. In case you see error messages about Windows Defender at startup, or you see failed updates in Windows Update, move here to resolve this issue.
Windows 8 and newer have a special, much-improved version of Windows Defender (or Windows Defender Security Center in Windows 10 Creators Update and later) that provides full real-time protection just like Microsoft Security Essentials. Therefore you cannot install Security Essentials in Windows 8 and later.
Because running more than one anti-virus program at the same time makes your computer slow, it is very important to first uninstall the currently present one. If you do not have an anti-virus program installed, move down here.
Click the Start button or press Windows Key on your keyboard to open the Start menu. Then type "remove" into the Start menu Search box and click Add or remove programs.
Find the anti-virus program you want to remove, right-click on it and then click Uninstall or Uninstall/Change (depending on the options the program provides). Then follow the uninstall wizard to remove the program. You probably have to restart your computer after this. You will also see the Action Center flag icon with a red cross in the Taskbar Notification area, this is normal because you have temporarily no antivirus program installed.
Open the Microsoft Security Essentials download page and choose the correct file: 14 megabytes is for 64-bit (x64) Windows 7, 11 megabytes is for 32-bit (x86) Windows.
Remember, you cannot install MSE in Windows XP and Vista!
After downloading and launching the setup file, Microsoft Security Essentials Installation Wizard starts, click Next.
License Terms page opens, click I accept.
If you are very-very concerned about your privacy, do not join the Customer Experience Improvement Program. Choose I do not want to join the program at this time and then click Next.
Next, the setup file offers to optimize security by enabling Windows Firewall in case it is turned off and no other firewall program is installed and active. In most cases, you can leave the If no firewall is turned on, turn on Windows Firewall (recommended) checkbox ticked.
Put a checkmark in the Turn on automatic sample submission checkbox to send suspicious file samples to Microsoft for further analysis automatically. This prevents somewhat annoying pop-ups from appearing - and do not fear, no personal information will be sent.
Now setup is ready to install Microsoft Security Essentials. Click Install.
The installation part takes a little while. After it is complete, leave the Scan my computer for potential threats after getting the latest updates box checked and click Finish. This will open Microsoft Security Essentials, start an update process, and then run a quick scan (around 10 minutes long).
That's it for the installation part.
If something seems to be blocking the installation, run RKill to terminate malware processes and services that might interfere with downloading or installing Microsoft Security Essentials. Then retry the installation again, without rebooting your PC.
If Microsoft Security Essentials' icon remains yellow-orange for a long time, it could mean that there is an upgrade to the program available. Click the icon and then click Open.
In the main window, there should be a message "A new version of Microsoft Security Essentials is available. You should upgrade now". Click the big Upgrade now button.
User Account Control pops up. Click Continue or Yes to continue with upgrade:
Microsoft Security Essentials Upgrade Installation Wizard opens. Click Upgrade.
In the License Terms page, click I accept.
Again, if you are very concerned about your privacy, click I do not want to join the program at this time to reject the Customer Experience Improvement Program. Then click Next.
The upgrading might take several minutes to complete. After the new version has been installed, you will see the following screen. Click Finish.
And this completes the upgrade.
In some cases, Windows Defender displays an error message after starting or restarting your computer. The "Windows Defender is turned off" message can be safely ignored by clicking Close. Remember, Microsoft Security Essentials actually replaces Windows Defender in Windows 7 and therefore the older service is not allowed to start anymore.
If you try to start the Windows Defender service manually, you'll see the "Windows Defender service on Local Computer started and then stopped" dialog. Click OK. You might also see some failed updates in Windows Update in case Windows Defender is still enabled.
The dialog on computer startup appears because the Windows Defender service is set to start automatically. To stop the message from appearing again, follow the steps below:
- Open the Start menu and type "services" into the Search box. Click Services.
- Find and right-click Windows Defender service. Select Properties from the menu.
- Set Startup Type to Manual. Click OK to close the service properties window.