How to Repair Windows Defender

by Ty Arthur
lovely business lady 3 image by Paul Moore from

The Windows Defender software constantly scans your computer for threats such as spyware that may slow down your computer or try to steal personal information. If the software wasn't installed properly or is conflicting with other programs running on your machine, Windows Defender may not work correctly. To repair the software you either need to download the latest update available for the program, or you need to completely uninstall and reinstall Windows Defender.

Step 1

Restart your computer's operating system. Double-click the "Windows Defender" icon in the system tray at the lower-right end of the screen.

Step 2

Click the question mark icon at the top of the Windows Defender screen and choose "Check for Updates." Select "Continue" if you are running Windows Vista. Wait for the updates to finish installing and click "Scan."

Step 3

Click "Stop Scan" if the problem persists. Click the question mark icon again and select "Exit Windows Defender." Click "Yes" to confirm you want to close the software.

Step 4

Open the "Start" menu screen and select "Control Panel." Select "Uninstall a Program" in Windows 7 or Windows Vista, or instead choose "Add or Remove Programs" in Windows XP.

Step 5

Click the "Windows Defender" entry and select "Uninstall." Choose "Yes" and restart the computer after the program is removed.

Step 6

Navigate to the Windows Defender installation webpage (see Resources). Click "Download" and double-click the Windows Defender installation file when it downloads to your hard drive.

Go through the onscreen installation instructions. Open the "Start" menu and choose "All Programs." Select "Windows Defender." Click "Scan" to start a new scan for malicious software.


  • Windows Defender will only work properly in Windows XP if you have Service Pack 2 or later installed. If the service pack is not installed, navigate to the "Start" menu and choose "All Programs." Click "Windows Update" and follow the onscreen instructions to install the latest service pack.


  • Windows Defender may not work properly or may cause your computer to experience slow performance if you are also running another anti-spyware or antivirus tool. Right-click the system tray icon for the other program and choose "Exit." Only run a single real-time antivirus or anti-spyware program at once. If you need to use more than one tool, ensure any other tools are turned off first.


Photo Credits

  • lovely business lady 3 image by Paul Moore from

About the Author

Ty Arthur has been writing technical and entertainment-related articles for a variety of online sources since 2008. His articles have appeared on and many other websites. Arthur attended the Great Falls College of Technology and studied both computer science and creative writing.

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