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Help please with Windows Defender

skaggsje's Avatar

Join Date: Feb 2014
Posts: 2,033

04-13-18, 01:28 PM   #1  
Help please with Windows Defender

My Windows Defender turned it self office. I can't restart it.

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PJmax's Avatar
Group Moderator

Join Date: Oct 2012
Posts: 42,481

04-13-18, 02:24 PM   #2  
What operating system are you running ?

~ Pete ~

Bob14525's Avatar

Join Date: Jun 2013
Posts: 1,228

04-13-18, 02:56 PM   #3  
Have you tried rebooting the computer? This same thing happened to me the other day. Rebooting the computer solved the problem.

Fred_C_Dobbs's Avatar

Join Date: May 2010
Posts: 300

04-14-18, 12:15 PM   #4  
If it's refusing to start for you, there might be a discoverable reason or it might just be another of Micro$loth's "undocumented features." One problem that could cause Windows Defender not to start is a mis-set system time. If you don't know how to force the system to update, it's "supposed to" update system time at each reboot (and I use that term advisedly, because you already see evidence the system isn't behaving as it's "supposed to"). So following Bob14525's advice just might fix everything that's wrong.

If your system time is okay (and unless something else has gone wrong), you should be able to start defender from Command Line. Press and hold the Windows key (that's the one with the Micro$loth flag on it). While holding the WinKey, press the 'R' key. That will open the 'Run' applet, which will have a small window labeled "Open" that can accept command line input. Cut-and-paste the following line into that window, then press the Enter key.

%ProgramFiles%\Windows Defender\MSASCui.exe

Commands issued from the 'Run' window automatically are run with Administrator privileges, which is preferable for jobs like this to running the command from a regular Command Prompt.

You also might try a System Restore. A restore will take system files back to an earlier point in time but doesn't bother your personal files. I use it all the time for quirkies like this I can't find a solution to.

Open the 'Run' applet again and enter:


That will start the System Restore applet. Read the directions of each step carefully. Individual restore points will be identified according to the date they were made on. I'd suggest you use the most recent restore point available before you first noticed the problem. If that doesn't fix it, use the most recent one before that (each time backing up one more restore point in time). The process is reversible so if something has gone wrong with the restore, it "should" (and there's that word again) offer you the opportunity to 'undo' the restore.

Last edited by Fred_C_Dobbs; 04-14-18 at 01:43 PM.
skaggsje's Avatar

Join Date: Feb 2014
Posts: 2,033

04-15-18, 01:23 PM   #5  
Thank You PJ, BOB and Fred. So far so good.

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