I found this in a few different places around the 'net - hopefully it's helpful:

Install the Recovery Console on Your Computer

You can install the Recovery Console as an option on your startup menu and use it to recover your system in the event that safe mode and other startup options don?t work. This tool is for advanced users.

• With Windows XP running, insert your Windows XP CD in the drive, and click Exit when the installation options are displayed.
• Click Start, click Run, and then type D:\i386\winnt32.exe /cmdcons Where D: is the CD-ROM drive letter, and then press Enter. (There is a space between .exe and the slash.)
  
• Follow the instructions on screen to install the Recovery Console, and when the installation is complete, restart your computer. The Recovery Console will show up in the list of available operating systems in the Startup menu. You must be an administrator to use the Recovery Console.
  If the i386 directory is already installed on your computer (as might be the case in computers purchased with Windows XP pre-installed), you can use the same syntax as in Step 2, using the [path]\i386 directory without having to use the CD.

An alternative method is to boot to the CD and start WINNT.EXE, then when prompted to Install or Repair, click Repair, which installs the Recovery Console for you.

If Windows XP will not start, you can run the Recovery Console from the Setup CD.