Microsoft Windows XP Service Pack 3 (SP3) provides new proactive security technologies for Windows XP to better defend against viruses, worms, and hackers along with increased manageability and an improved experience for users.
Microsoft Windows XP Service Pack 3 fixes a range of bugs in Windows XP. It doesn’t matter what XP updates you have previously applied to your system, SP3 will update any unpatched, partially patched or completely updated system (it includes all previously released patches and updates). XP SP3 fixes the security holes so you won’t get attacked.

Microsoft periodically combines updates, fixes, and other improvements into a single package - Service Pack. Microsoft develops updates, fixes, and other improvements that address issues reported by the company’s customers and partners. To make it easier for customers to get these updates and enhancements, Microsoft periodically combines them into a single package, and makes that package available for all Windows customers.

Download:  Windows XP Service Pack 3 Build 3300 RC2