How to fix system scan error on Windows 8?

Open a command prompt with admin rights and run this DISM command to detect and repair corrupted files on the HDD:

DISM /Online /Cleanup-Image /RestoreHealth

This is the advanced version of sfc /scannow. Windows now downlaods the corrupted files from the Internet instead of telling you that the files can't be repaired. 


http://blogs.technet.com/b/joscon/archive/2012/09/26/fixing-component-store-corruption-in-windows-8-and-windows-server-2012.aspx

This is a windows of command.com:


"Microsoft Windows [Version 6.3.9600]
(c) 2013 Microsoft Corporation. All rights reserved.

C:\Windows\system32>sfc /scannow

Beginning system scan.  This process will take some time.

Beginning verification phase of system scan.
Verification 100% complete.

Windows Resource Protection found corrupt files but was unable to fix some
of them. Details are included in the CBS.Log windir\Logs\CBS\CBS.log. For
example C:\Windows\Logs\CBS\CBS.log. Note that logging is currently not
supported in offline servicing scenarios.

C:\Windows\system32>DISM /Online /Cleanup-Image /RestoreHealth

Deployment Image Servicing and Management tool
Version: 6.3.9600.17031

Image Version: 6.3.9600.17031

[==========================100.0%==========================]
The restore operation completed successfully. The component store corruption was
 repaired.
The operation completed successfully.

C:\Windows\system32>"