Using the Emergency Repair Disk to Fix Windows NT Problems

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By Ronald Nutter, MCSE, MCNE

Published in TechRepublic's Windows NT Help Desk Report

The feature-rich nature of Windows NT 4.0 can be both a blessing and a curse. On one hand, all those features make NT 4.0 an incredibly powerful operating system. On the other hand, they make recovering from a system failure a little more complicated than it used to be. It's no longer as simple as booting from a basic boot disk and running the sys command to restore a workstation's or server's boot sector—now, you also have to work with NT's boot files, as well as the registry and security files.

That's where your Emergency Repair Disk (ERD) comes in. No system administrator's bag of tricks is complete without this simple but effective tool. In this article, we'll fill you in on how the ERD does its job. We'll also show you how to create the disk, and we'll address a couple of considerations for using it.

The Way It Works

When one of your workstations experiences a system failure, you need to be able to do two things right away. First, you must be able to reboot, either by using the NT CD (if you have it) or by using setup disks you've created previously (see the sidebar "Options for Rebooting.") Second, you have to analyze what went wrong and develop a strategy for recovery. That's where the ERD comes in.

By default, the ERD will initiate a repair process that inspects the registry files and the startup environment, verifies the Windows NT system files, and inspects the boot sector. NT will then let you know which files you can use to repair any problems found. This process should address most of your recovery needs, so you won't have to purchase one of the commercially available NT utility packages.

Creating The ERD

Now that you know you need an Emergency Repair Disk for each workstation, how do you create it? Simple: with a basic tool called RDISK.

Place a blank formatted disk in the floppy drive. Next, choose the File | Run menu item and type RDISK /S. (The /S option skips the Create Repair Disk dialog box and proceeds directly to saving the NT workstation configuration.) That's all there is to it. (Note: When you create an Emergency Repair Disk, label it immediately. And, to avoid confusion, be sure the label clearly indicates which machine you used to create that particular disk.)

Using The ERD

To use the ERD, you'll first need to boot the workstation using either a startup disk set you've created (see the sidebar "Options for Booting") or the NT CD. When you get to the screen that asks you to press [Enter] to install Windows NT or press [R] to repair a damaged Windows NT installation, insert the ERD and follow the onscreen directions. By default, the ERD will proceed with the repair process described earlier. Depending on your configuration, the process may take several minutes.

How Up To Date Is Up-To-Date Enough?

Obviously, for an ERD to be of any use, you must keep it up to date. But how often do you need to update it? For the most part, this is a judgment call for the user or administrator to make. Theoretically, any time anyone changes a workstation's configuration or installs an application, you should update the workstation's ERD.

If that isn't a realistic approach for your network, you'll need to weigh the information your company can afford to lose against the information that can be recreated with reasonable efficiency. Those factors should tell you how often you need to update each workstation's ERD.

Options For Rebooting

Before you can use your Emergency Repair Disk (ERD), you must boot the machine. If you're lucky, you'll have a Windows NT CD on hand, which you can use to reboot without incident. But a couple of circumstances can make things the process more difficult.

For instance, if the workstation came with an OEM preinstall of NT, you may not have a CD to work with. In that situation, you have two options. The best solution is to be prepared: Invest the $20 or so it takes to buy a CD version of NT, so you'll have it on hand should disaster strike. Your other option is to create the three floppy disks necessary to boot the machine. To do so, go to the I386 directory and run WINNT32 using the /OX option.

Another scenario: You have an NT CD available, but the machine doesn't support booting from CD-ROM. In that case, you can put the NT CD into the CD drive and run WINNT32 with the /OX option to create the three boot disks. As the boot diskettes are created, label them according to the onscreen instructions.

Depending on the number of machines you have and the variety of configurations that exist, you may need to create more than one set of boot diskettes. It's a good idea to have at least one additional set, just in case a disk in the primary set happens to go bad when you need it.

If you use any special controllers or other devices to boot your NT workstation or server (particularly any that NT doesn't support out of the box), you should have at least one copy of the driver disk that came with that device—you'll need it when booting the workstation from the startup disk set. When the hardware discovery screen appears and lists the devices found so far, simply follow the instructions to have NT load additional drivers to continue with the booting process.

Other Handy Uses For An Emergency Repair Disk

The ERD isn't limited to fixing corrupted registry files. You can also use it to repair problems that originate with changes made to the registry with REGEDIT or a similar utility. In some situations, the solution is to insert or delete a key or change the value of an item in the registry. The downside to making registry changes is that you may make the problem worse or make the system unbootable or otherwise unstable.

An up-to-date ERD will also prevent gray hairs when you need to reset the password to a previously used one. It can save you many hours you might otherwise spend reinstalling Windows NT and the associated programs on the workstation being recreated.


No single tool can save the day in every situation, but the Emergency Repair Disk is a formidable ally when trouble strikes. With an Emergency Repair Disk for each workstation on hand, you may save yourself the headache of a total reinstall of Windows NT.

Ron Nutter is a senior systems engineer for Lextech, Inc., a systems integration firm in Lexington, Kentucky. He's a MCSE, Novell Master CNE, and Compaq ASE. Ron is currently working on installing a 9-state, 31-office WAN utilizing NT, Netware, and AS/400s for a national utility. He's also the Help Desk Editor for Network World. You can reach Ron at

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