A Microsoft Windows NT utility for updating information in the %SystemRoot%\repair folder and creating an emergency repair disk (ERD). You can use the ERD to save the configuration of a server running Windows NT and to restore the server if the system files or registry become corrupted. Rdisk is not listed as a Windows NT administrative tool, but you can run it from the command prompt, from the Run command box (via the Start menu), or by creating a shortcut to the executable by using the path \Winnt\System32\rdisk.exe.
When you run rdisk, you can either update the \Winnt\Repair directory or simply create an ERD. (You can create a Windows 2000 ERD from the Welcome tab of the Backup tool.)
Rdisk.exe normally doesn’t back up the default, Security Account Manager (SAM), or security hives unless you run it with the /s switch. To do this, type rdisk /s at the command prompt or in the Run command box.