Both file manipulations can have a severe impact on system stability. The SFC Scannow command recovers Windows system files so that their current version is replaced with the original file.

SFC, which means System File Checker, scans all protected Windows files and replaces corrupted, damaged, missing and changed versions with the correct versions.

The sfc /scannow command needs to be issued from an elevated command line prompt. Here is how this is done:

Click on the Start Menu orb, then all programs and locate the
Command Prompt entry in the Accessories directory (in Windows 7, other operating systems vary).

Right-click the command prompt and select to Run as Administrator from the context menu.

The system scan will be initiated after issuing the command. It will take some time and the verification process is displayed in the command line window.

The system file check may require access to Windows media files from the original installation source to replace or copy the original files.

It has to be noted that the command will replace all modified files even those that have been modified deliberately by a user of the system (e.g. a patched uxtheme.dll file to be able to use third party themes).

Not everyone likes to use a command line version (that comes with several parameters) on the other hand. File Checker is a small portable software program that offers a GUI for the process. The program gives the system administrator the tools at hand to run most sfc commands from that GUI including starting a system scan, purging the cache or defining the locations of the setup sources.

Options are available that can change the process further. It is possible to reset the cache size to a new value, to disable the Windows File Protection and to define how protected system files should be handled by the scan.

The Windows XP system file checker is a portable alternative for system administrators who like to work with graphical user interfaces. File Checker is available at the developer’s website.