In such cases, Windows Defender fails to start, which basically means that it does not offer any protection whatsoever to the computer, and even though Microsoft Security Essentials is always up and running, its Spyware & Unwanted Software Protection and Virus Protection are both turned off. When the user tries to turn the disabled protection options on, a Microsoft Security Client dialog pops up displaying the following error message: “An error has occurred in program initialization. If this problem continues, contact your System Administrator. Error Code: 0x80070426.” While error code 0x80070426 usually refers to a non-genuine copy of Windows, in this case, the error refers to MSE not working correctly. When error 0x80070426 appears, it leaves your computer completely vulnerable as Windows Defender doesn’t even start up and MSE doesn’t work properly. The solution to this problem is to simply uninstall Microsoft Security Essentials, allowing Windows Defender to do its job and protect your computer. The following are all of the steps you need to follow in order to fix error 0x80070426. Hold the Windows Key and Press R. Type taskmgr in the run dialog. Locate the Windows Defender Service (WinDefend), right click on it and choose Stop.
This should stop the Service, but it will start automatically after the computer reboots. While it is stopped; you can uninstall Essentials. Normally in such cases, you cannot uninstall Microsoft Security Essentials because Windows Defender is programmed to block the installation AND un-installation of Microsoft Security Essentials. However, you should be able to uninstall Microsoft Security Essentials as though it were any other program now since the Windows Defender has been temporarily disabled. To uninstall it; go to Control Panel -> Programs & Features -> Uninstall a Program or Hold the Windows Key and Press R; type appwiz.cpl and Click OK, locate Microsoft Essentials and Uninstall it. Then, Restart your computer. After the reboot and removal of Essentials; Go to Settings -> Update & Security, Choose “Windows Defender” and make sure Real-time protection is on. Now go back to Task Manager -> Services tab and make sure that the Defender service is running.
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