Today my computer decided to start a boot loop where it claimed that WdFilter.sys was missing or damaged.
The file looked ok when inspected from the command prompt option of the Windows Recovery Environment (WRE). However in this same environment the option to fix startup issues continued to fail.
Restoring Restore points in the same WRE failed as well. The restore went well, the result was the same boot loop again.
Next try was to try-out all start-up modes from bootlog, safe mode etc. All resulting in the same boot loop. Strangly enough did the option to skip early virus scanning (of which WdFilter.sys seems a part as ‘Wd’ in WdFilter.sys seems to stand for Windows Defender).
Finally, in a last attempt before a reset of Windows, I decided to make a bold move and just rename the WdFilter.sys (which resides in the ‘C:\Windows\System32\drivers\wd‘ folder) to WdFilter.old and re-run the system start up repair option in the WRE.
To my surprise: Windows suddenly restored a correct copy of the filter driver and Windows booted correctly.
No guarantee but as it’s easily reverted (renaming WdFilter.old back to WdFilter.sys) trying might not harm.
But as it worked in my case I felt I should share this method.
Note: Only drawback so-far is that the renamed file can’t be deleted from within Windows due to file protection.