It is similar to deploying Windows Vista/Server 2008/7.
1. Add the default Windows 2008 boot image to WDS.
2. Create Capture Boot Image and add it to boot image.
3. Create a Windows XP reference computer (install the operating system, applications, and make any other changes).
4. Sysprep it.
5. PXE boot the reference computer into capture image on the boot screen and then capture the image.
6. Upload the captured image to WDS server.
7. Clients can PXE boot and select the Windows XP install image to install Windows XP now.
For detailed information, please refer to the following article:
Step-by-Step Guide for Windows Deployment Services in Windows Server 2003
This article is similar to the WDS deployment process in Windows Server 2008 and it includes how to deploy Windows XP through WDS.
Hope it helps.