Here's how
To do an unattended installation you must create an Answer File. It contains all the info that XP will need, allowing you to be away from the computer while setup takes place.
CREATING THE ANSWER FILE:
1. First you must install the Deployment Tools. This is located on the Windows XP Home or Windows XP Professinal disk; location \Support\Tools.
Double click the Deploy.cab file. Select all the files in this compressed folder and copy them to a folder on your hard disc.
2. One of these files is the Windows Setup Management Wizard (Setupmgr.exe). Run this wizard.
Select the following as they appear at the prompt:
-- Create a new answer file
-- Windows Unattended Installation
-- Windows XP Home or Professinal, depending on which you wish to install
-- Fully automated
-- No, this answer file will be used to install from a CD
-- Accept the Liscense Agreement
Now you must complete the answer file. Highlight items on the left column and set the appropriate settings in the right pane. Be sure to have you XP CD key handy for this.
At the Computer Name be sure to use the 'Add' button to the right if you create your own computer name.
Finally, click 'next' to name and save the answer file to a safe location on your drive or removable media (the default name is Unattend.txt). Saving it to a floppy drive makes it especially easy to use if you plan to install from CD.
USING THE ANSWER FILE:
Easy Way -- If your computer can boot from the Windows XP Professional or Home Edition CD, save the answer file on a floppy disk and name it Winnt.sif. Insert the CD and the floppy disk and turn on the computer. Setup runs from the CD and uses Winnt.sif as its answer file.
Setup Manager Wizard's Way -- Setup Manager creates a batch file using the same file name (but with a .bat extension) and location that you specified for the answer file. Simply navigate to the folder where you saved the answer file and open the batch file. If you copied the batch file, the answer file, or both from the location where Setup Manager originally stored them, you might need to edit the batch file to update the path information. Simply right-click on the batch file (.bat) and then choose 'edit' from the context menu.
Command Line Way -- Include the /Unattend switch (along with the file specifications for the answer file) on the command line for Winnt32.exe, the Windows XP Setup program. For example, if you're installing from the Windows XP Professional CD and you want to use an answer file named Unattend.txt that's stored on a floppy disk, enter this command line:
d:\i386\winnt32 /unattend:a:\unattend.txt
MORE ON THE ANSWER FILE:
The Setup Manager Wizard guides you through the most commonly used settings. If you want to be more comprehensive with your automated installations you can open Ref.chm, which is the online reference guide that is included as part of the Deployment Tools collection. This HTML Help file provides a complete reference to all the answer file parameters in the Unattend.txt section.
This information has been paraphrased from the book Windows XP Inside Out