Windows Defender error 577 in Windows 8.1

[Fawn]

I am using a touch screen pc with Windows 8 on it. I recently downloaded Windows 8.1 from its store and installed it properly on my computer. But after that when I am trying to open Windows Defender, then it will give me error message that says "Error 577: Windows cannot verify the digital signature for this file". I dont know how to turn Windows Defender on again, so if anyone knows how to do this please let me know? Thanks

[DanielV]

There was a solution for this issue but you will have to edit your registry editor for that. First of all press the Windows key + R and then type regedit and press Enter key. After that go to these 2 registry keys - HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Microsoft\Windows Defender and HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows Defender and change the value of 'DisableAntiSpyware' and 'DisableAntiVirus' from 0 to 1. Once changed then go to this location C:\Program Files\Windows Defender and open MSASCui.exe file, thats it.

[Solomon]

If the above solution doesnt work for you then you might be having trouble with the NIS driver in your computer. So, to solve this you can try to do a clean boot and see if that helps. Swipe in from the right edge of the screen, and then tap Search. Or, if you are using a mouse, point to the lower-right corner of the screen, and then click Search. Type msconfig in the search box, and then tap or click msconfig. On the Services tab of the System Configuration dialog box, tap or click to select the Hide all Microsoft services check box, and then tap or click Disable all.On the Startup tab of the System Configuration dialog box, tap or click Open Task Manager. On the Startup tab in Task Manager, for each startup item, select the item and then click Disable. Close Task Manager. On the Startup tab of the System Configuration dialog box, tap or click OK, and then restart the computer. More information is given here - http://support.microsoft.com/kb/929135

[Enriqueta]

I also had this similar kind of problems but was able to solve this on one of my computers that was running on Windows 8.1 operating system. The problem was with the Service which was not started although the registry was set to on. Later on the solution was just to go to action center and then turn its services to on. This solution has worked out for me. I also did a clean up of my system before doing this, so you could also try all my suggestions to fix your problem.