At the elevated cmd prompt can you enter
net start trustedinstaller to see what that reports, also go to services.msc from Start and the Windows Module Installer should be set to Manual, but you can click on it then on Start in the upper left pane.
If it isn't showing as Manual, right click on it and select Properties then use the dropdown to change its status then click on Start - OK
After either, retry the sfc /scannow.
If that still fails to run, enter
chkdsk /f and follow the prompt to type
y for it to run after the next reboot.
The cmd
shutdown /r /t 00 will effect an immediate restart then wait for it to do its thing.
I don't know if you've run a chkdsk before, but it will briefly display its report on screen before the reboot.
If you miss it you can view its full report in Event Viewer by going Start - type
eventvwr and press enter.
When it has read the data, expand Windows Logs, click on the name Applications/Action/Find then type
chkdsk or
wininit into the Find box and press enter.
Cancel the Find box and read the report in the scrollable window.
If that still fails and you have a Win 8.1 install disk, then you can run the sfc /scannow outside of Windows by following the bit to Run the Offline System File Checker in
http://www.thewindowsclub.com/run-system-file-checker-safe-mode-boot-timeIf you don't have a Win 8.1 install disk then this article will show you how to create one
https://www.winhelp.us/non-destructive-reinstall-of-windows-8-and-8-1.htmlWhile the first article doesn't say, you will need to change the Boot order, either in the BIOS (Setup) or by tapping F12 (usually) as you switch on.
Use the cursor keys to select the media type, insert the media and press enter if you are using F12.
Before entering the offboot sfc cmd, enter
bcdedit |find "osdevice" and use that partition letter in the cmd.
That's a Pipe symbol before
find and is the upper case of \