Windows XP SP1 and SP1a support ends on October 10, 2006 [support.microsoft.com] Microsoft will end support on this date. This also includes security updates for these service packs. Microsoft is providing final notifications to customers regarding the end of support for these products.
Microsoft is ending support for these products as part of the Microsoft Support Lifecycle Service Pack support policy. We recommend that customers who are still running Windows XP SP1 or SP1a upgrade to Windows XP Service Pack 2 as soon as possible.