Windows Defender application failed to initialize Error code 0x800106ba

Windows Defender is a free antivirus software from Microsoft. The program is well known for its reliability, effectiveness, and stability but, occasionally it might turn nonfunctional, displaying the error code 0x800106ba with a short description – Windows Defender application failed to initialize.

Windows Defender

Error Code 0x800106ba Application failed to initialize

Why does this problem arise? Well, some third-party software installations cause a conflict with Windows Defender. Running two security software can also create such problems. Sometimes, the DLL files from the utility are not registered properly. They too can cause the problem.

To fix this issue, you can try the following:

  1. Run services.msc to open the Services Manager and ensure that the Windows Defender service to Automatic.
  2. Re-register Windows Defender DLL files

Re-register Windows Defender DLL files

We will be telling you how to re-register the Windows Defender DLL files here. Open a Command Prompt window, type “regsvr32 file name” and hit Enter.

CMD window

You have to re-register each of these dll files. So for each of these files, replace “file name” in step 1 with each one of these, one after the other and hit Enter.

regsvr32 wuaueng.dll
regsvr32 wucltui.dll
regsvr32 softpub.dll
regsvr32 wintrust.dll
regsvr32 initpki.dll
regsvr32 wups.dll
regsvr32 wuweb.dll
regsvr32 atl.dll
regsvr32 mssip32.dll

Restart and see if it has helped you. You may also see if this Microsoft Fix It 9779673 helps you.

Windows Defender is turned off or not working may also interest you.

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Anand Khanse is the Admin of, a 10-year Microsoft MVP Awardee in Windows (2006-16) & a Windows Insider MVP. Please read the entire post & the comments first, create a System Restore Point before making any changes to your system & be careful about any 3rd-party offers while installing freeware.