The following are recommended recovery options for computers running Windows NT 4.0 with Service Pack 4 and later installed:

•	Use the Uninstall feature by selecting Windows NT 4.0 Service Pack 4 or later in Control Panel - Add/Remove and clicking the Remove button.
•	Run an Emergency Repair with an emergency repair disk (ERD) that was created with rdisk /s after installing Service Pack 4 or later.
•	Run an Emergency Repair with the Repair folder on the boot drive.

The following methods can be modified to repair an installation:

•	Do an Emergency Repair using an emergency repair disk created prior to Service Pack 4.
•	Do an upgrade of Windows NT 4.0 over Windows NT 4.0 with Service Pack 4 or later installed. For example, when the system restarts after the text-mode portion of Setup is complete, select the Upgrade option rather than the New or Repair options.

Because of changes in the registry's SAM and Security Hives, the Samsrv.dll, Samlib.dll, Winlogon.exe, Lsasrv.dll, Services.exe, and Msv1_0.dll files have changed, and previous versions of these files cannot access Windows NT system security information after Service Pack 4 or later is applied. If pre-Service Pack 4 versions of the first three files are present, you may not be able to log on and, instead, receive a pop-up error message referencing the STOP code 0xC00000DF (that is, the specified domain name does not exist). If the pre-Service Pack 4 versions of the last three files are present, you may receive a driver entry point failure in Lsasrv.dll.

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Uninstalling the Service Pack

If an administrator can log on to the computer and run an application, uninstall the service pack by running the Add/Remove Programs tool in Control Panel, selecting Windows NT 4.0 Service Pack 4 or later, and clicking the Remove button. This is always the preferred method of recovery. When using the uninstall feature, the computer is restored to the system configuration as it was directly before applying the service pack. If the computer stops responding (hangs) during startup, this is not a viable option.

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Using an ERD Created After Installing the Service Pack

The Windows NT 4.0 Service Pack 4 and later installation modifies the Setup.log file in the Repair directory on the system to reference the correct checksum value for the 6 files that need to match the Sam and Security registry files. This lets you run the repair procedure and repair system files and only try to repair the six files if they do not match the checksum value for the Service Pack 4 and later versions. The registry files are not updated in the Repair directory until you run the Rdisk program. The SAM and Security hives are not updated unless you run Rdisk with the /s parameter. If the Service Pack 4 and later versions of the six files are on the system but the registry files are restored from the repair information before Service Pack 4 and later are installed, the registry files will be updated on system startup.

For more information about rdisk, please see the following article in the Microsoft Knowledge Base: NOTE: To use the Emergency Repair procedure, you must have the updated version of Setupdd.sys. The updated version is contained in Service Pack 2, 3, and 4 and later. To update your version of Setupdd.sys, you must copy Setupdd.sys from the service pack to your installation disk 2. This replaces the previous version of Setupdd.sys with the updated version.

For more information, please see the following article in the Microsoft Knowledge Base: Repairing the Windows NT system files will replace the current files on the system with files from the Windows NT 4.0 installation media. This ensures recoverability for users where the system has become unstable after the application of the service pack. If a service pack is required, it must be reapplied when the Emergency Repair is completed and the system has restarted. This method should only be used if the system is in an unbootable state.

If, when running the repair procedure and inspecting the System files, it prompts to repair Samsrv.dll, Samlib.dll, Winlogon.exe, Lsasrv.dll, Services.exe, or Msv1_0.dll, you can either repair them and replace with the Windows NT 4.0 media versions or choose not to repair these specific files. If you still cannot start the system, you can either replace these files manually with Service Pack 4 and later versions by starting to another installation on the computer that can access the file system of the volume containing these system files or modify the Setup.log file on the emergency repair disk to replace the files with Service Pack 4 and later revisions with the following procedure:

1.	Make a duplicate copy of the emergency repair disk before modifying because this procedure may keep the repair procedure for fixing other problems.
2.	Remove the attributes from the Setup.log file by typing the following at the command prompt: attrib -r -h -s a:\SETUP.LOG
3.	Add the following lines under the [Files.WinNt] section of the Setup.log file: \Winnt\System32\Samsrv.dll = "samsrv.dll"," 30ec0","\","nt40 repair disk","samsrv.dll" \Winnt\System32\Samlib.dll = "samlib.dll","f993","\","nt40 repair disk","samlib.dll" \Winnt\System32\Winlogon.exe = "winlogon.exe"," 3c2eb","\","nt40 repair disk","winlogon.exe" \Winnt\system32\lsasrv.dll = "LSASRV.DLL","2e7c7","\","nt40 repair disk","lsasrv.dll" \Winnt\system32\services.exe = "SERVICES.EXE","2e740","\","nt40 repair disk","services.exe" \Winnt\system32\msv1_0.dll = "MSV1_0.DLL","cca6","\","nt40 repair disk","msv1_0.dll" NOTE: \Winnt represents the folder where Windows NT is installed.
4.	Copy Samsrv.dll, Samlib.dll, Winlogon.exe, Lsasrv.dll, Services.exe, and Msv1_0.dll from the Windows NT 4.0 Service Pack 4 and later media to the root folder of the emergency repair disk. NOTE: If there is not enough room on the ERD for the file you are replacing, any files other than Setup.log can be deleted from the ERD to make room. This makes the ERD unusable for other repair functions, so keep the original ERD in a safe place. You can also use a second disk containing the file to be replaced and insert it when prompted for the "nt40 repair disk".
5.	Restart your computer with the three Windows NT 4.0 setup disks.
6.	Select "R" to Repair your Windows NT installation.
7.	Select "Verify Windows NT System Files" and continue.
8.	If prompted to insert Windows NT setup disk 4, press ESC to continue with the Repair process.
9.	Replace any of these files when prompted.
10.	Reboot the computer and restart Windows NT.

For more information on this procedure, please see the following article(s) in the Microsoft Knowledge Base:

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"Upgrading" Windows NT 4.0 Over Windows NT 4.0 with Service Pack

NOTE: If you had to use Service Pack files to install originally, these files will need to be used during this upgrade procedure. For example, if you used the SP4 atapi.sys to access an ide drive larger than 8GB, follow the procedure in the following article in the Microsoft Knowledge Base: If the computer is unable to start and the repair process fails or you do not have an emergency repair disk or a CD-ROM drive, you must perform an upgrade of Windows NT 4.0 over Windows NT 4.0 Service Pack 4 and later. Please follow these steps to do this:

1.

Copy the i386 folder from the original Windows NT 4.0 CD-ROM to the hard disk of the target system if FAT, or to a network share if NTFS. In this folder, rename the following files. Copy these same six files to the I386 directory from the Service Pack 4 and later source. The goal is for the upgrade to be done using these six files from Service Pack 4 and later. Samsrv.dl_ to Samsrv.org Samlib.dl_ to Samlib.org Winlogon.ex_ to Winlogon.org Lsasrv.dl_ to Lsasrv.org Services.ex_ to Services.org Msv1_0.dl_ to Msv1_0.org

2.

Choose the correct procedure below based on your file system: • If the file system is FAT and the i386 folder is on the local hard disk, perform the following steps: a. Start to MS-DOS and run WINNT /B from the i386 folder. b. Choose the Upgrade option during the first start into the GUI mode. • If the install source location is remote and the local file system is FAT, you must either install Windows with networking enabled, or create an installation boot disk off the Windows NT Server CD-ROM, connect to the modified i386 folder, and then run WINNT /B. • If the file system is NTFS, you must create a parallel install in a new folder and then run WINNT32 /B from the modified i386 folder.

NOTE: The Winnt32.exe and Setupdd.sys files are not included with the downloadable versions of Service Pack 4 and later(they are on the CD-ROM).

The Setupdd.sys file is available for download from the following location:

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