Microsoft/Windows Update Program Manager Nate Clinton has just posted on an issue we've learned of that affects some users of Windows Update repairing their systems using a Windows XP CD. The symptom is that some Windows XP customers are unable to install updates via the latest version of Windows Update after using a Windows XP CD to perform the "Repair from CD" function.
The issue does not look to be widespread and occurs in rather exceptional only under specific circumstances; it occurs because the Windows XP Repair CD replaces all system files, including Windows Update, with older versions of those files. Meanwhile, the most current version of Windows Update (which is already present on the system) includes a file that is not present in the Windows Update image on the Repair CD. After performing the repair, the new file remains on the system and creates a registry mismatch, causing subsequent installation of some updates to fail.
Luckily, there is a remedy: customers experiencing this issue can 1) refer to KB article 943144; 2) check Nate's post for work-around steps now; or, 3) contact Support using the telephone number(s) found at support.microsoft.com/security (usually found in the right-hand nav).