Support for Windows XP Service Pack 1 ends October, 2006

According to the Microsoft Support Lifecycle, Windows XP Service Pack 1 (SP1) and Service Pack 1a (SP1a) on will reach its end of life on October 10, 2006. This is a significant announcement as this will also end any further security updates for anyone using these service packs; subsequently, any computer using SP1 or earlier will be at risk for exploits. (Source: sysadmin.it)

If you are still running SP1 or SP1a, it is recommended that you upgrade to Windows XP Service Pack 2 as soon as possible.

How to Determine Which Service Pack is Installed on your System

To determine which service pack is installed on your system, right-click My Computer, and then click Properties. If "Service Pack 1" appears under System, you are running Windows XP SP1. Note that it is not recommended that you install SP1a if you are already running SP1 (instead, upgrade to Service Pack 2: free from Microsoft).

Note, however, that Service Pack 2 is notorious for not installing properly. In this case, you may want to download Dennis's XP Service Pack 2 Guide which provides a number of failsafe procedures to guarantee a proper installation.

Windows XP Service Pack 3

Microsoft expects to release Windows XP Service Pack 3 sometime in mid to late 2007. Aside from the important cumulative list of bug fixes, Service Pack 3 will also include Internet Explorer 7, Windows Media Player 11 and a few other applications. (Source: softpedia.com)