System File Checker (SFC.exe)
System File Checker scans the operating system files and when it finds a corrupted file it prompts the user to restore the original file. It uses a file called Default.sfc to insure that the system files have not been changed. Default.sfc contains checksum data (the binary sum of the file's contents), date, time, size, and version information. Default.sfc can be updated to reflect changes in the existing system files when newer versions of the system files are flagged.
System file checker can be used to extract a single system file from the windows cabinet files, when one is known to be missing or corrupt.