Being prompted for the source when no files are being reinstalled is due to a bug in the Windows Installer patching algorithm.
The unnecessary prompting for the original installation source when you apply a Windows Installer patch is improved in Windows Installer version 2.0. In Windows Installer 2.0, you may be prompted for the original installation source when applying a patch.
Any of the following conditions can cause a prompt for the original installation source:
- If the feature to be patched has components with unversioned files that are not modified on the computer, Windows Installer requires the source unless the unversioned files are authored in the appropriate MsiFileHash table entries in the original setup package.
- When you call the ResolveSource Windows Installer standard action from a custom action during the patch application requires the original source.
- When you call the ResolveSource Windows Installer standard action in the original product setup during the patch application requires the original source.
- If the feature to be patched is currently set to Run-From-Source.
Setting a feature to run from source implies that the feature does not have to be installed locally and should run from the original installation source.
- The cached .msi file for the product that is being patched is missing from the machine. This can happen if the files under the computer %windir%\installer directory are erroneously deleted by an end user or software program.
Windows Installer 2.0 Redistributable for Windows 95, Windows 98, and Windows Millenniium Edition