Can a corrupted file be repaired by the Windows Installer?

A corrupt file will not trigger Windows Installer to perform a self-repair. This is because the Windows Installer checks only for file existence when checking a component that uses a file for its keypath. Read on to learn more.

Although a corrupted file may not function properly, as long as Windows Installer can verify that the file exists at that location a self-repair will not be triggered. However, if another missing keypath causes a self-repair the corrupted file will be replaced with a functioning copy from the installation source if the file is in the same feature as the component with the missing keypath.

Corrupted files can be repaired by performing a manual repair of the .MSI using the maintenance dialog or by running the MSI via command line with the switch /focmus. Additionally, the following information must be true for the repair to correct the corrupt file:

1. The file must have a internally provided checksum provided. This is done at compile time of the .DLL, .OCX, or .EXE by the program used to create that file.
2. The Attribute column of the File table for this file must include the attribute '1024' which indicates to the Windows Installer service that the file has a valid checksum. To look at this table, select the Setup Editor, then the Tables tab. This attribute may need to be added manually to the attribute column.