Recovering from a system crash is never an enjoyable experience, but Windows 2000 goes a long way to lessen the pain. The latest version of Windows Safe Mode allows you to troubleshoot boot problems more effectively than ever before, and Sfc.exe finally allows you to restore protected system files.

The Safe Mode boot options are troubleshooting modes that load Windows 2000 with a minimal set of device drivers and services. After you start Windows 2000 in Safe Mode, you can use troubleshooting techniques such as running System File Checker or restoring backups to resolve the problem.

For more information about the Safe Mode boot options and other advanced startup options, see Microsoft Knowledge Base article Q202485, "Description of Safe Boot Mode in Windows 2000" (http://go.microsoft.com/fwlink/?LinkId=3052&ID=202485).

Warning
The following article involves editing your system registry. Using the Windows Registry Editor incorrectly can cause serious problems requiring the reinstallation of your operating system and possible loss of data. Use the Registry Editor and the following directions at your own risk.

Operating systems prior to Windows 2000 don't provide protection for shared system files such as dynamic link libraries (DLLs). That makes it possible for an application to install an older version of a DLL or executable and cause hung applications or problems with the OS. Windows 2000, on the other hand, provides a level of protection against system changes through the Windows File Protection (WFP) feature. WFP maintains a signature catalog of protected files. WFP checks the file's version when a protected file is modified (typically through an application installation). If the file isn't the correct version, WFP restores the correct file from the Dllcache folder or distribution media as needed, prompting you to provide the source file (such as the Windows 2000 CD).

At the completion of the GUI-mode portion of Setup, Windows 2000 uses a tool called System File Checker (Sfc.exe) to scan all protected system files and verify the existence of the appropriate signature catalog files. If a catalog is corrupted or doesn't exist, SFC restores the catalog from the cache or from the distribution media, again prompting you for the CD if necessary.

Use SFC at any time to scan the system for protected system file changes and to re-create the Dllcache folder if it's damaged or corrupted.