A silent update that Microsoft deployed widely in July and August is preventing the “repair” feature of Windows XP from completing successfully.

Ever since the Redmond company’s recent download of new support files for Windows Update, users of XP’s repair function have been unable to install the latest 80 patches from Microsoft.

Repaired installations of XP can’t be updated

The trouble occurs when users reinstall XP’s system files using the repair capability found on genuine XP CD-ROMs. (The feature is not present on “Restore CDs.”) The repair option, which is typically employed when XP for some reason becomes unbootable, rolls many aspects of XP back to a pristine state. It wipes out many updates and patches and sets Internet Explorer back to the version that originally shipped with the operating system.

Normally, users who repair XP can easily download and install the latest patches, using the Automatic Updates control panel or navigating directly to Microsoft’s Windows Update site.

However, after using the repair option from an XP CD-ROM, Windows Update now downloads and installs the new 7.0.600.381 executable files. Some WU executables aren’t registered with the operating system, preventing Windows Update from working as intended. This, in turn, prevents Microsoft’s 80 latest patches from installing even if the patches successfully downloaded to the PC.

I was able to reproduce and confirm the problem on a test machine. When WU tries to download the most recent patches to a “repaired” XP machine, Microsoft’s Web site simply states: “A problem on your computer is preventing the updates from being downloaded or installed.” (See Figure 1.)

Figure 1. After a repair install of XP, which resets the operating system to its original state, Windows Update can’t install the 80 most-recent patches from Microsoft.

Most ordinary Windows users might never attempt a repair install, but the problem will affect many administrators who must repair Windows frequently. Anyone who runs XP’s repair function will find that isolating the cause of the failed updates is not a simple matter.

Beginning in July, it is not possible for Windows users to install updates without first receiving the 7.0.6000.381 version of nine Windows Update support files. If Automatic Updates is turned on, the .381 update will be installed automatically. If AU is not turned on, you’ll be prompted to let Windows Update upgrade itself before you can installing any other updates. Consequently, users are forced to get the silent update before they can attempt to install Microsoft’s latest security patches.

The problem apparently arises because seven of the DLLs (dynamic link library files) used by WU fail to be registered with Windows. If files of the same name had previously been registered as happened when Windows Update upgraded itself in the past the new DLL files are registered, too, and no problem occurs. On a “repaired” copy of XP, however, no such registration has occurred, and failing to register the new DLLs costs Windows Update the ability to install any patches.

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