TRANSFORMS An advantage to using Windows Installer (MSI) as a packaging and deployment mechanism is that it supports a common technique for customizing an MSI database, namely through the use of transforms. A transform, or .mst file, is a Windows Installer file that contains changes to an MSI database to be applied when the MSI package is installed When deploying an installation, you specify the transform(s) to apply to a product using the MSI property TRANSFORMS. (As with other MSI properties, the property name TRANSFORMS is case-sensitive.) Note that a transform cannot be launched by itself, and cannot be applied to a product already installed on the target system. Using the TRANSFORMS Property To apply a transform to a product when installing from the command line, you populate the TRANSFORMS property with a semicolon-separated sequence of transform names. The simplest example is the following command: msiexec /i SampleApp.msi TRANSFORMS=SampleAppChanges.mst You can also specify multiple transforms by separating their names with a semicolon, as in the following: msiexec /i SampleApp.msi TRANSFORMS=T1.mst;T2.mst Transforms are applied to the MSI database in the order you specify. If there is any overlap between the transforms you specify, the data in transforms specified later in the list (T2.mst, in the command above) will override data in transforms specified earlier in the list (T1.mst). When you apply a transform to an installation as described above, the transform is cached on the target system. For a per-machine installation, the transform is cached in the directory%2