Windows XP SP1 and SP1a support ceased on October 10, 2006
Final customer notifications about the end of Windows XP SP1 and SP1a support

Support for Microsoft Windows XP Service Pack 1 (SP1) and Service Pack 1a (SP1a) ends on October 10, 2006. 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.

To determine whether you are running Windows XP SP1, right-click My Computer, and then click Properties. If "Service Pack 1" appears under System, you are running Windows XP SP1. We do not recommend that you install SP1a if you are already running SP1. We recommend that you install Windows XP SP2 if you are running Windows XP SP1 or SP1a.