Making Sure the System Always Starts

This section discusses the following three topics:

• Starting a system with configuration problems
• Reconstructing a system with damaged files
• Creating a custom startup verification program

The goal in all of these topics is to make sure a Windows NT system starts correctly each time you turn on the switch. The obvious preliminary steps, of course, involve planning ahead for system safety, with the following activities:

• Protect the Registry hive files on disk and maintain a regular backup program, including backups of Registry hive files, as described in "Maintaining the Registry" in Chapter 11, "Registry Editor and Registry Administration."
• Maintain a handy copy of the Emergency Repair disk created when you installed Windows NT. Each Emergency Repair disk works only for the computer where it was made during Setup.
• Install a redundant copy of the operating system to make the system more robust, as described in Chapter 3, "Customizing Windows NT Setup."

You can also rely on Windows NT to automatically recover from damages to startup data. Specifically, to protect from bad sectors occurring in the System hive file, Windows NT automatically creates a backup of the system hive named the SYSTEM.ALT file, which is stored in the SystemRoot\SYSTEM32\CONFIG directory. If any problems are encountered while reading the System hive during startup such as damage to the file, the Boot Loader automatically switches to the SYSTEM.ALT file to continue starting the system. For more information about the SYSTEM.ALT file, see "Hives and Files" in Chapter 10, "Overview of the Windows NT Registry."