mwb1100 - here you go, sp3 download on the microsoft site, googled win xp sp3 and the first link took me here
http://www.microsoft.com/downloads/details.aspx?FamilyID=68c48dad-bc34-40be-8d85-6bb4f56f5110&displaylang=enBrief Description
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.