Windows 2000 and Windows XP SP2 will reach the end of support on July 13th, 2010, for more information read: End of Support for Windows 2000, Windows XP SP2 and Windows Vista RTM
Please note, this end of support doesn't have any effect for the Windows XP 64 bit version.
There's no SP3 for the 64-bit version of Windows XP. If you're running the 64-bit version of Windows XP with SP2, you have the latest service pack and will continue to be eligible for support and receive updates until April 8, 2014.
Source : Learn how to install Windows XP Service Pack 3 (SP3)