What Is In Service Pack 3
Windows XP SP3 includes all previously released Windows XP updates, including security updates and hotfixes, and select out-of-band releases. For example, the service pack includes functionality previously released as updates, such as the Microsoft® Management Console (MMC) 3.0 and the Microsoft Core XML Services 6.0 (MSXML6).
Microsoft is not adding significant functionality from newer versions of Windows, such as Windows Vista, to Windows XP through XP SP3. For instance, Windows XP SP3 does not include Windows Internet Explorer 7, although Windows XP SP3 does include updates to both Internet Explorer 6 and Internet Explorer 7, and it will update whichever version is installed on the computer. One notable exception is that, SP3 does include Network Access Protection (NAP) to help organizations that use Windows XP to take advantage of new features in the Windows Server® 2008 operating system. For more information about Internet Explorer 7, visit http://www.microsoft.com/windows/products/...ie/default.mspx.
Knowledge Base article 936929 lists all other all Knowledge Base articles associated with updates that are included in Windows XP SP3. The following sections also provide a high-level description of the functionality included in Windows XP SP3.

Deploying Windows XP SP3
Windows XP SP3 will be available through Windows Update and the Microsoft Download Center. The service pack will also be available to Volume License customers, TechNet subscribers, and MSDN® subscribers. Through Windows Update, the download size varies, but it is typically 70 megabytes (MB), depending on the computer’s configuration. Through the Download Center, the download size is approximately 580 MB. Fundamentally, deploying Windows XP SP3 works the same as deploying SP1 and SP2 for Windows XP:
- SP3 is cumulative, so users can install SP3 on top of Windows XP SP1 or SP2.
- Windows XP SP3 supports the same languages as Windows XP did in its initial release.
- You can run the SP3 update package on any SKU of Windows XP SP1 or SP2. For example, you can run the SP3 update package on a computer running the Windows XP Media Center Edition with SP1.
- Tools and guidance for system administrators have not fundamentally changed from Windows XP SP2. For comprehensive information, visit the Deploy Windows XP Professional and Windows XP Service Pack 2 Deployment Information sites on Microsoft TechNet.
- You can deploy SP3 using Microsoft Systems Management Server 2003, Microsoft System Center Configuration Manager 2007, or third-party solutions. The process has not fundamentally changed.
Windows XP SP3 is for x86 editions of Windows XP only. The x64 editions of Windows XP were serviced by Windows Server 2003 SP2. For additional information, go to Windows Server 2003 Service Pack 2.

This hasn't been added to automatic updates yet, right? Because I didn't find it there.

Microsoft, for some reason, took their little packets off auto-update. I had to manually install SP2.

Windows XP SP3 will be available through Windows Update and the Microsoft Download Center. The service pack will also be available to Volume License customers, TechNet subscribers, and MSDN® subscribers. Through Windows Update, the download size varies, but it is typically 70 megabytes (MB), depending on the computer’s configuration. Through the Download Center, the download size is approximately 580 MB. Fundamentally, deploying Windows XP SP3 works the same as deploying SP1 and SP2 for Windows XP:

Interesting

Nice too see Microsoft still caring about XP

Windows XP Service Pack 3 (SP3) includes all previously released updates for the operating system. This update also includes a small number of new functionalities, which do not significantly change customers experience with the operating system.

I'm going to wait until Windows XP Service Pack 3 is finial not release candidate. Also MS didn't add it to Auto Updates because it is not final version it a Release Candidate, the version between beta and finial so it is still partly unstable.