Using an Emergency Repair Disk Created by Windows NT

During Windows NT installation, an Emergency Repair Disk (ERD) is created that includes the following:

• System Registry hive (SYSTEM._).
• Software Registry hive (SOFTWARE._).
• The Security Account Manager (SAM) and Security database registry hives (SAM._ and SECURITY._).
• Default user profile (default._).
• New user profile (ntuser.da_) Windows NT version 4.0 only.
• The Setup.log file.
• The Autoexec.nt file.
• The Config.nt file.

If something happens to your computer's hard disk drive to corrupt or change your startup system files or Windows NT registry, you can use the ERD to get the system back into a bootable state. After you restart the Windows NT operating system, you can then perform a full recovery by restoring from your last system backup.

For example, you have a computer running Windows NT that allows you to specify which operating system to start (MS-DOS or Windows NT) by using the boot loader menu. If the MS-DOS SYS command is inadvertently run on drive C, you will no longer be able to start (boot) Windows NT. You will only be able to start MS-DOS.

The boot loader is a small program that resides in the first physical sector(s) of the active partition. Windows NT stores the old boot loader code into a new file called Bootsect.dos. Windows NT replaces the boot loader sector with a new loader program stub. This new loader finds the NTLDR program and runs it. NTLDR switches into protected mode operation and loads a mini-file system, which then reads Boot.ini. Boot.ini presents the boot loader information used to start your system with Windows NT or MS-DOS. In the above example, when the SYS command was run from MS-DOS, the boot loader sector was overwritten by MS-DOS's boot sector. This MS-DOS boot sector does not know anything about Windows NT or boot loader.

Sample Repair Procedure

The procedure below explains how to recreate the Windows NT boot sector information, allowing the dual boot features to be reactivated using the ERD created during installation:

1. Start your computer using Windows NT Setup Disk 1, and then Disk 2.
2. At the first screen, press "R" for Repair.
3. You will see four selections. All four will be selected by default. Move the selector bar with the arrow keys to highlight the options. Press ENTER to select/clear the options.
   
   

      [ ]  Inspect registry files
      [ ]  Inspect startup environment
      [ ]  Verify Windows NT system files
      [X]  Inspect Boot Sector
   						

4. Select only the option "Inspect boot Sector" option. Move the selector bar to the line that says to Continue, and then press ENTER.
5. Let Windows NT perform the mass storage detection. If necessary select "S" to specify additional drivers if your computer requires Original Equipment Manufacturer drivers.
6. When prompted to do so, insert the ERD that was originally created for this computer. (Or press Esc to let Windows NT search for Windows NT 3.51 or 4.0 repair information)
7. Repair will run the CHKDSK utility, verify the boot sector, and then rebuild it if necessary.
8. You will be prompted to restart your computer when the process is complete.

When you restart your system, the Windows NT Boot Loader screen appears, allowing you to choose between MS-DOS or Windows NT.

Additional Sources of Information

For more information about using the Emergency Repair Disk, see: