When Microsoft Windows XP sp2 had too many updates. All those updates are now in one pack.
sp3 - 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.
If you cann't get it from Window Update site. still you can get from MicroSoft Directly
Read KB 936929