System File Checker (SFC) is a utility in Windows 7 and Windows 8.x that allows the user to repair missing or corrupted system files. This is done from an elevated command prompt from Windows, or if the system will not boot to Windows, then from the "Repair Your Computer" Boot option.
However, when a multiple boot configuration is used (2 versions of Windows installed on a single system) the System File Checker cannot see the operating system to repair.
Follow the instructions below for using SFC /scannow with the windows repair disk on multiboot configurations.
The following steps will allow you to boot to a Windows Repair Disk then run the SFC /scannow command on the appropriately assigned drive.
sfc /scannow /offbootdir=d: /offwindir=d:\windows
then press the Enter Key to execute the command.https://support.microsoft.com/en-us/kb/929833