Windows - windows\system32\drivers\ngelam.sys missing, or corrupt

ELAM recovery

By default, it is the responsibility of the 3rd party AV service to store a copy of the ELAM driver in the registry defined backup location, from where a copy of the ELAM driver can be obtained, in case the original file gets corrupted.

This is usually the path C:\Windows\ELAMBKUP defined in registry location HKLM\SYSTEM\CurrentControlSet\Control\EarlyLaunch via reg_key BackupPath