A System File Checker is an extremely useful tool that will scan all protected Windows system files and replace corrupted files with a cached copy that is located in a compressed folder at %WinDir%\System32\dllcache. This is useful for fixing a large variety of problems, especially when dealing with Windows boot issues.
An SFC scan is generally ran directly from the drive that Windows is on (usually C:). In these cases, the command is very simple:
But what if I need to initiate an SFC from a drive other the one Windows is on?
There is such a thing as an offline SFC scan. This function allows an SFC scan to point to a Windows drive that is different than the drive which the command is being ran from. This means an SFC can be started from a WinPE or WinRE environment which usually runs off the ram drive X:.
There are a few additional parameters needed for an offline SFC scan:
sfc /scannow /offbootdir=C:\ offwindir=C:\Windows
The /offbootdir should be whichever drive Windows is on, and the /offwindir should point to the Windows directory on that same drive.