This is an error code associated with the Windows Defender software. As this is a software product that helps combat malware then if you get this error code then your computer is probably infected with malicious software.
The first thing to try with regard to this error is to attempt to clean the registry of your computer. A good way to do this is to download the Total System Care, which will do an excellent job of cleaning your registry, although more action will be required once this has been completed.
More Information and Manual Resolution
If Windows Defender will run then the first thing to try is updating the program and then running a scan of your whole system. If you are getting this error code, of course, then it is highly unlikely that this will be possible.
There is usually no easy workaround to this issue as your malware and virus programs are essentially disabled by this error. However, one thing to attempt before you fret too much is to restore your computer to a time when it was working correctly.
System restore can be accessed through the Start menu, by simply typing “System Restore” into the search box.
If the system restore utility will not run correctly then you can attempt to activate safe mode. To run Windows in Safe Mode, restart your computer and press F8 (if you have Windows installed). Once you’ve reached the desktop in Safe Mode, type ‘System’ into the Start search box and press Enter once ‘System Restore’ is highlighted. You should then be able to run the system restore utility.
In many cases, this will make no difference to the error code, as malware and viruses can be pretty difficult to shift. If this is the case then it is advisable to try downloading HitmanPro 3.7 (v18.104.22.168-Beta) with Kickstart 2.2. This program will detect and removes these reparse points enabling Windows Defender to run again.