Checking Critical System Files
System files can be corrupted for a variety of reasons, including improper system shutdown, problems with disk media, or a new application improperly overwriting a necessary driver with its version. In Windows 98, Windows ME, Windows 2000 and Windows XP, the Windows File Protection (WFS) system is used to minimize this. The WFP system tracks all changes to system files and makes sure that any new files assigned to replace a protected file are valid. It also sends a message to the system administrator when an improper file replacement of one of these protected files is attempted.
The WFP system includes the System File Checker (SFC) utility, which can be run at the command prompt to verify the versions of all system files under protection and reload saved copies from a hidden cache. The SFC reports any files that do not match the SFC default.sfc file. If you know a specific system file shown on the list is corrupt or missing or you expect it is the cause of some problem, you can extract it from the Windows installation disk using the SFC Extract option. In SFC, choose Extract One File From Installation Disk, enter the full filename when prompted, and click Start. Then give the program the location of the disk with the file and where you want it to be copied. When you click OK, the SFC extracts the file to the desired location.