Windows XP Service Pack 3 Network Installation Package for IT Professionals and Developers
http://www.microsoft.com/downloads/details.aspx?FamilyId=5B33B5A8-5E76-401F-BE08-1E1555D4F3D4

This installation package is intended for IT professionals and developers
downloading and installing on multiple computers on a network. If you're
updating just one computer, please visit Windows Update.


Release notes for Windows XP Service Pack 3
http://support.microsoft.com/kb/936929