Microsoft continually works to improve its software. As part of this effort, we develop updates and fixes to recognized issues and release them for customers. On a regular basis, we combine many of these fixes into a single package and make the package available for customers to install on their computers. These packages are called Service Packs. read more ... Windows XP Service Pack 1 (SP1) provides the latest security, reliability, and performance updates to the Windows XP family of operating systems. Windows XP SP1 is designed to ensure Windows XP platform compatibility with newly released software and hardware, and includes updates that resolve issues discovered by customers or by Microsoft's internal testing team.

Windows XP Service Pack 1 can be downloaded for free or ordered on CD beginning September 9th. according to the offical SP1 homepage