How to Turn On Windows Defender

Uninstalling a Third-Party Antivirus Program

1. 
   Determine whether you intentionally installed an antivirus program. If you did install an antivirus program on purpose, you should know its name. If not, another program probably installed the antivirus software as part of its installation process, meaning you'll need to look for a program whose name you don't recognize.
2. 
   Open Start

   

   . Click the Windows logo in the bottom-left corner of the screen.
3. 
   Open Settings

   

   . Click the gear-shaped icon in the bottom-left corner of the Start menu. The Settings window will open.
4. 
   Click Apps. It's in the middle of the Settings window.
5. 
   Sort by date if necessary. If you don't know the antivirus program's name, you can narrow it down by showing the most recently installed programs and working backward from there. To do so, click the "Sort by" menu, then click Install date in the drop-down menu.

   1. If you know the antivirus program's name, skip this step.
6. 
   Find the antivirus program. Scroll through the list of installed apps until you find the program that you need to uninstall.

   1. If you didn't intentionally install an antivirus program, you'll probably find the program you need to uninstall near the top of the list of programs if your Windows Defender only recently turned off.
7. 
   Click the program's name. Doing so expands the program's name to display an Uninstall button.
8. 
   Click Uninstall. You'll find this under the program's name.
9. 
   Click Uninstall when prompted. Doing so opens the program's uninstallation window.
10. 
    Follow the uninstallation prompts. Click through the on-screen uninstall prompts, making sure to select the "Delete all files" (or similar) option if asked whether you want to keep residual files and apps.
11. 
    Delete other associated programs. Some antivirus programs install additional programs to handle things like web security; if you see other programs which come from the same developer or have similar names to the program you just uninstalled, uninstall them as well before proceeding.
12. 
    Restart your computer. Click Start

    

    , click Power

    

    , and click Restart in the pop-up menu. Your computer will restart like usual, after which point your Windows Defender program should be back up and running.

    1. If Windows Defender doesn't turn back on after your computer finishes restarting, you can try turning it on manually.