|At this link click "Steps to take before you install SP 3"|
What is Service Pack 3 ?
Windows XP Service Pack 3 (SP3) is a free update for Windows XP. SP3 includes all previously released Windows XP updates,
including security updates, hotfixes, and select out-of-band releases.
Free unlimited installation and compatibility support is available for Windows XP, but only for Windows XP SP3, until April
14, 2009. Chat and e-mail support is available only in the United States and Canada.