Windows Defender fails to Open - error

I need your help please. Windows defender doesn't want to open and I have no virus/spam software running. I think the problem was caused by some new malware.

When I click the defender icon on desktop or cpanel:
Windows cannot access the specified device path, or file. You may not have the appropriate permissions to access them.

When I try to force open defender in C:\Program Files\Windows Defender, I get this message
MSASCui.exe: Windows cannot access the specified device, path or file. You may not have the appropriate permissions to access the item. (Most .exe in this directory give that message)

When I go to services.msc, I see that Window Defender service is not started. On clicking start, I get this error message:
Windows could not start Windows Defender Service service on local computer. Error 14105: The size of the manifest exceeds the maximum allowed.

Windows Defender Network is also stopped and cannot be started (Error 5: access denied)

Hope you can be able to help me to solve this issue.
Thank you in advance

IF it helps I ran rkill.exe and gave out this log:

Code:

Rkill 2.8.4 by Lawrence Abrams (Grinler)http://www.bleepingcomputer.com/
Copyright 2008-2017 BleepingComputer.com
More Information about Rkill can be found at this link:
 http://www.bleepingcomputer.com/forums/topic308364.html


Program started at: 02/03/2017 07:52:09 AM in x64 mode.
Windows Version: Windows 10 Home 


Checking for Windows services to stop:


 * No malware services found to stop.


Checking for processes to terminate:


 * C:\Windows\SysWOW64\dxconfig.exe (PID: 3408) [WD-HEUR]
 * C:\Windows\SysWOW64\dxconfig.exe (PID: 10392) [WD-HEUR]


2 proccesses terminated!


Checking Registry for malware related settings:


 * No issues found in the Registry.


Resetting .EXE, .COM, & .BAT associations in the Windows Registry.


Performing miscellaneous checks:


 * Modified HKCU\...\Winlogon: [Shell] => explorer.exe,"C:\Users\Steven\AppData\Roaming\clientmonitor.exe"


 * No issues found.


Checking Windows Service Integrity: 


 * gagp30kx [Missing Service]
 * IEEtwCollectorService [Missing Service]
 * IoQos [Missing Service]
 * nv_agp [Missing Service]
 * TimeBroker [Missing Service]
 * tunnel [Missing Service]
 * uagp35 [Missing Service]
 * uliagpkx [Missing Service]
 * WcsPlugInService [Missing Service]
 * wpcfltr [Missing Service]
 * WSService [Missing Service]


 * agp440 [Missing ImagePath]


 * AJRouter => %SystemRoot%\system32\svchost.exe -k LocalServiceNetworkRestricted [Incorrect ImagePath]
 * WpnService => %systemroot%\system32\svchost.exe -k netsvcs [Incorrect ImagePath]


 * vmicrdv => %SystemRoot%\System32\icsvcext.dll [Incorrect ServiceDLL]
 * vmicvss => %SystemRoot%\System32\icsvcext.dll [Incorrect ServiceDLL]


Searching for Missing Digital Signatures: 


 * No issues found.


Checking HOSTS File: 


 * HOSTS file entries found: 


  127.0.0.1    localhost
  ::1    localhost
  127.0.0.1    activation.acronis.com


Program finished at: 02/03/2017 07:52:38 AM
Execution time: 0 hours(s), 0 minute(s), and 28 seconds(s)

I had this error with Windows7/Security Essentials a number of years ago, I used a free tool from Microsoft (Microsoft Safety Scanner) to fix the problem.

Once downloaded I ran a Full Scan

Thank you Tairiku - yes I suspect some malware messed up some parts of my Win10 - I started receiving lots of spam recently. I opted to start automatic Distributed Link Tracking Client and after a reset it is running. Still Defender is dead.

VFR Rider, I'm downloading MS Safety Scanner and let you know what happens. I am also trying Antibyte Malware too.

Is it possible to uninstall defender completely and re-install it - maybe that solves the problem.

Marz said:

.

Is it possible to uninstall defender completely and re-install it - maybe that solves the problem.

No. If your scans are negative, consider a System Restore to a point before the problem.

Since your system has actually been unprotected, I would do a System Reset. Your files can be saved. May have to reinstall some addons and software.

Check the tutorials above if not familiar with Restore or Reset process.

Malware bytes found 90 threats and removed them (but I saw that mostly were cookies)
Microsoft Safety Scanner has far found 10 infected files and still running

I hope my Acronis backup was done before the infection - that would save me.
System restore is not an option I think.
Reset PC my last hope!

Will keep you informed
Just to say thanks

Unfortunately still without Windows defender. Is there a way to learn what is messed up ? I think that I do not have any virus now, but need to recover the 'damage' inflicted by the malware of which at least one was to deactivate defender. Otherwise I do not have any other issue.

I think that I found at least part of the problem. I have the registry \software\microsoft\windows defender disableantispyware and disableantimalware set to 0 where I read it must be 1. When I try to set it to 1, I get an ownership error. I also read that this is fixed by the tool regownit - but I still can't get ownership and possibly I am using wrong this tool. Any help please tp set this to 1

Windows Resource Protection did not find any integrity violations.