This content is 20 years old. I don't routinely update old blog posts as they are only intended to represent a view at a particular point in time. Please be warned that the information here may be out of date.
Johan Arwidmark has published some undocumented unattend.txt entries for unattended Windows installations.
Recent versions of the Microsoft Windows Preinstallation Reference (ref.chm), which covers Windows XP and Windows Server 2003 include the additional [Components] entries which Johan identifies, but not the [Unattended] entries. For reference, the version I’m looking at is dated 10 August 2004 and ships with Windows PE 1.5.