Backup SAM Database

Found this article in the Knowledgebase:
When you use the /s command-line switch with the Rdisk.exe tool, the Sam._ and
Security._ database files are copied to the %SystemRoot%\Repair folder and to
the ERD. If your repair information exceeds the capacity of a single floppy
disk, you may not be able to use the /s command-line switch when you create the
ERD.

To create an ERD without copying the Sam._ and Security._ database files, run the
Rdisk.exe tool with no command-line switches. Use the Update Repair Info option,
and click Yes when you are prompted to create an ERD.

For additional information about the /s command-line switch, see the following
article in the Microsoft Knowledge Base:

Q122857 : RDISK /S and RDISK /S- Options in Windows NT

If you used the /s command-line switch with the Rdisk.exe tool, the Sam._ and
Security._ databases were copied to your %SystemRoot%\Repair folder. You may be
able to create an ERD by using an older version of these files. If you have a
version of the Sam._ and Security._ files from an earlier backup or ERD, copy
them to the %SystemRoot%\Repair folder. Run the Rdisk.exe tool, use the Update
Repair Info option, and click Yes when you are prompted to create an ERD.

NOTE: If you use an older version of your Sam._ and Security._ files when you
repair your Windows NT installation, you may lose user account and machine
account information.

You can get free backup software from: http://www.bos.co.il or http://www.axave.com

The SAM database is made up of two files called "sam" and "security".
They are located the winnt\system32\config folder