Windows – How to run msiexec from cygwin to unpack a msi

See: Special Installation Instructions for the ActiveGanttVBA & ActiveGanttCSA Gantt Scheduler Components

To circumvent this error, extract and double click on the:

Install_As_Administrator.reg

File that is included in the Install_As_Administrator.zip file distribution that can be downloaded from the top link on this page. This file will modify the Windows Registry to include the following information:

[HKEY_CLASSES_ROOT\Msi.Package\shell\runas]
@="Install &As Administrator..."

[HKEY_CLASSES_ROOT\Msi.Package\shell\runas\command]
@="msiexec /i \"%1\""

Once the Windows Registry has been modified using the Install_As_Administrator.Reg patch you can right click on any Windows Installer (*. msi) file and select the option Install As Administrator and the .msi file will run using elevated permissions (Administrator Permissions).

You can uninstall it using the product code:

msiexec.exe /x {your-product-code-guid}

You would obtain this code from the MSI itself, or whatever tool you are using to build the MSI.

Note that when you uninstall a product, it uses a cached MSI, since only the original MSI knows how to uninstall itself. When you use the product code, it uses the cached MSI from C:\WINDOWS\Installer.