SFC is deprecated, use dism instead

Often sfc.exe reports errors that it cannot resolve automatically.
Instead of "sfc.exe /scannow" run as Administrator:

1. Dism /Online /Cleanup-Image /ScanHealth
2. Dism /Online /Cleanup-Image /CheckHealth

this will report healthy, repairable or non-repairable.

If it reports repairable run the following:

1. Dism /Online /Cleanup-Image /RestoreHealth

For offline Images (including the recovery environment):

1. Dism /Image:C:\offline /Cleanup-Image /RestoreHealth

Note: The needed files are pulled dynamically from Windows Update so you need to have Internet access. If you have any WSUS pollicies applying, disable all of them for the affected client and make sure it updates the policy. I'm not kidding, it fails if it windows updates isn't the update source. I don't know why, but I've seen it happen.