Windows® XP Service Pack 3 (SP3) includes all previously released
updates for the operating system. This update also includes a small
number of new functionalities, which do not significantly change
customers’ experience with the operating system. This white paper
summarizes what is new in Windows XP SP3.
http://www.microsoft.com/downloads/details.aspx?FamilyID=68c48dad-bc34-40be-8d85-6bb4f56f5110&DisplayLang=en