During Windows NT 4.0 Setup, you are given the option to create an Emergency Repair Disk (ERD). Microsoft recommends that you create an ERD during Setup so that you will have the proper tools in case fault recovery becomes necessary.  

Maintaining a current ERD is just as important as having a current system backup. When system configuration changes are made (such as installing new software or changing software configuration, altering network configuration, hardware changes, operating system updates) you should update your ERD with the Rdisk utility included with Windows NT.

A current Emergency Repair Disk is your most valuable tool in recovering information that you need to start your system. The Emergency Repair Disk is intended to provide just enough recovery to restore a system to a bootable state and is not a replacement for regular backups.

Windows NT Server and Windows NT Workstation include the RDISK command for building and maintaining repair information. You can use this tool to update the repair information stored in the Winnt\Repair folder and to copy the information to a floppy disk. You can use the Emergency Repair Disk to replace damaged system files, restore damaged or incorrect registry information, and rebuild the startup environment.

You should update the repair information and create a new Emergency Repair Disk any time you change the system configuration in any significant way. For example, if you add or remove hardware from the system or change the disk drive configuration, you should update the repair information.

To maintain your current registry configuration, you must update your ERD. Otherwise, each repair disk only contains the registry information from the time Windows NT was first installed. To create an updated ERD, use one of the following methods: 

Type rdisk /s in the Open box. 

Type rdisk in the Open box, and then click Update Repair Info