You receive a "The upgrade patch cannot be installed by the Windows Installer service because the program to be upgraded may be missing" when you try to install a BizTalk Server 2004 service pack or other product update

When you try to install a Microsoft BizTalk Server 2004 service pack or another product update, the installation fails and you receive an error message that is similar to the following:

This issue can occur if the language version of BizTalk Server 2004 that is stored in the registry does not match the language version of the service pack or the update that you are installing. This language version mismatch occurs if you have previously installed a BizTalk Server 2004 product update and that product update was for a language version of BizTalk Server that is different from the language version of BizTalk Server 2004 that is installed.

Versions of BizTalk Server 2004 product updates that were released before January 2005 do not perform language version checking. Instead, they set the language version of BizTalk Server 2004 that is stored in the registry to the same language version as the update that is being installed.

All BizTalk Server 2004 product updates that have been introduced after January 2005 perform language version checking. These updates will not install if the language version of BizTalk Server that is indicated in the registry does not match the language version of the update. This issue persists even if the mismatched update is subsequently uninstalled.

To resolve this issue, contact Microsoft Product Support Services.

This behavior has been specifically observed to occur if you install a product documentation update that was released before January 2005 and if the update did not match the language version of BizTalk Server 2004 that was on the computer that was being updated.