Don't know if this helps but:
A Microsoft Knowledge Base article titled Description Of the System File
Checker Tool describes the tool as follows: The System File Checker
checks for damaged or replaced system files and then prompts you to
replace any files that do not match the original Win files.
This Description if accurate but not complete. The SFC does scan each system
file and compares it with the original Win system file, if the file is different
It assumes that the file has been damaged or replaced, but makes no distinction
between the two. It then prompts you to replace the different file, leaving you
to wonder: Is this file actually corrupt or has it been updated in a legitimate way,
say as a result of a Windows Update or the installation of a new software application
or device? If its the latter, you could easily overwrite a perfectly good file with an
older file that will disrupt or even cripple the operation of newer software or hardware
you have installed.
Check out this link:
http://www.updatexp.com/scannow-sfc.html