Thank you for registering me.
I have used Windows 8.1 for years with no problem.
Lenovo Desktop - CPU 3.6 GhZ - 8gb Ram - 1tb Drive - Only Windows 8.1 installed, no other OS.
Then this week, Defender stopped working.
On services.msc, it's on Automatic, but when I click on Start, I get "Windows could not start the Windows Defender Service service on Local Computer. Error 14105:The size of the manifest exceeds the maximum allowed"
If I try to start Defender from the Control Panel, I get "Windows cannot access the specified device, path, or file. You might not have the appropriate permissions to access the item".
I am Administrator and I am the only using the PC.
I have run Microsoft MRT -> no problem.
AdwCleaner -> no problem
Rkill -> no problem
FRST64 -> no problem.
RogueKiller -> no problem
All I have in StartUp is peerblock (I know it's old) and Malwarebytes anti-exploit 188.8.131.52
I ran CCleaner several times - version before the last one because Monitoring is stuck otherwise (known bug)
Windows updates and all drivers are up to date.
I tried to run Combofix but it displays "This operating system is not supported ... ... Windows 2000 is no longer supported"
I don't really want to use Avast / AVG etc, nor do I wish to reformat the drive nor reinstall Windows.
Everything works fine except Defender.
Could someone help me, please?