emergency repair disk (ERD)

ERD, Emergency Repair Disk, is a recovery tool for repairing missing or corrupt files or restoring the registry on a Microsoft Windows system.

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What is ERD (Emergency Repair Disk)?

A recovery tool for repairing missing or corrupt files or restoring the registry on a Microsoft Windows NT or Windows 2000 system. Having a current copy of the emergency repair disk for each server on your network is an important part of preparing for disaster recovery.

How it works

An emergency repair disk (ERD) contains compressed versions of registry hive, default user profile, setup.log, and other system configuration files. An ERD can be created any time using the rdisk utility, and should always be created after installing new services or software or upgrading hardware or device drivers on a system.

An ERD cannot be used to boot a computer running Windows NT or Windows 2000. To perform a system recovery of a machine running Windows NT using an ERD, boot your system using the three boot floppies and select the Repair option from the appropriate menu. Then select the specific repair options you want to perform, namely

  • Inspect Registry Files:
    Prompts to replace each registry file


  • Inspect Boot Sector:
    Restores Windows NT boot sector


  • Inspect Startup Environment:
    Restores the boot.ini file to allow access to Windows NT


  • Verify Windows NT System Files:
    Replaces missing or corrupt operating system files


To perform a system recovery on a machine running Windows 2000, try booting to Safe Mode first by pressing the F8 function key during startup. If this fails or if the system cannot be repaired, boot the system using the four boot floppies, select the Repair option by pressing the R key when prompted, and then either use the ERD to attempt a repair or press C to open the Recovery Console.

The Recovery Console is a powerful command-line interface to the operating system, designed for use by advanced administrators only.


If you can’t find your three Windows NT boot floppies, you can create a new set by running the command

from the Windows NT compact disc on a working computer running Windows NT. To create the four Windows 2000 boot floppies, insert the Windows 2000 compact disc and a blank floppy into any machine running MS-DOS or Windows, click Start, select Run, and enter the following path into the Run box:

<cdrom_drive>\bootdisk\makeboot a: