All the details you need are here and is available on Windows Update

Windows XP Service Pack 3 Resources

Blog post announcing RTW

Windows XP Support Forum

Windows XP SP3 TechNet portal

· Windows XP Service Pack 3: What is new and how to deploy This white paper summarizes what is new in Windows XP SP3, and how to deploy the service pack.

· Windows XP Service Pack 3 Release Notes

· Installing Windows XP Service Pack 3