Windows Defender is a free antivirus available from Microsoft, which is natively embedded in the latest versions of Windows (including Windows 8, 8.1 and 10).
In this way, Microsoft sought to ensure that all computers have a line of basic security against malware threats.
As a rule, whenever you install an antivirus, Windows Defender is automatically disabled. This happens, because it is not recommended to have two AntiVirus installed at the same time. Nevertheless, you can re-enable the Windows Defender on your computer with relative ease.
How to enable Windows Defender
As already mentioned, it is not possible to install two antivirus on your computer (However, you can use Malwarebytes Anti-malware to obtain a second opinion).
To remove an antivirus program you will need to use the AppRemover. If you have any questions, see our tutorial: how to remove antivirus (completely).
Then, press the shortcut keys CTRL + SHIFT + ESC to start Task Manager and go to the “file” menu-new task. In the dialog box that appears type “services.msc” (without quotation marks). Locate the Windows Defender service and with the right mouse button, go to “Properties”.
In the “General” tab, set the startup type to “automatic”. If the service is stopped, click the “start” button.
Are you having trouble activating Windows Defender? Try the following procedure. Start by accessing the Task Manager by pressing the shortcut keys CTRL + SHIFT + ESC. In the dialog box that appears type “regedit” (without quotes).
In registry editor navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defend directory
In the window on the right click with the right mouse button and select the option “Create Dword value (32 bit)” under the name DisableAntiSpyware, which must have the value zero.