Microsoft has released a script to allow the download of Windows XP Service Pack 3 Release Candidate 2 from Windows Update
Download the script and run it on a machine currently running Windows XP Service Pack 2. The script sets a registry key on your system. The registry key is required for Windows Update to recognize your machine as a valid target for Windows XP Service Pack 3 RC2.Windows XP SP3 RC2
Versions of Windows XP Service Pack 3 prior to Release Candidate 2 should be removed before attempting to use the registry key. Windows Update will not offer Release Candidate 2 to machines with previous versions of the Windows XP Service Pack 3 beta.
It is recommended that you apply the resulting update package to an activated, genuine copy of Windows XP, in a test environment. As with any pre-release software, it is also recommended that you back up files and settings on your machine before applying this update package.
