When error 0x80070426 appears, it leaves your computer completely vulnerable as Windows Defender doesn’t even start up and MSE doesn’t work properly. While error code 0x80070426 usually refers to a non-genuine copy of Windows, in this case, the error refers to MSE not working correctly. If this problem continues, contact your System Administrator. “An error has occurred in program initialization. When the user tries to turn the disabled protection options on, a Microsoft Security Client dialog pops up displaying the following error message: 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. However, in approximately 10% of all Windows 10 upgrades, something goes wrong and Windows Defender fails to replace Microsoft Security Essentials, resulting in the OS that is installed having both Microsoft Security Essentials and Windows Defender. When you upgrade from a previous version of Windows to Windows 10, Windows Defender takes over and replaces Microsoft Security Essentials. As of Windows 10, Microsoft Security Essentials is no more and the onboard defender for Windows users is a program called “Windows Defender”.
