Summary
Many installation packages have adopted a script-driven MSI for their software packaging. When an InstallScript MSI installation is deployed, the file Setup.exe needs to be deployed with the MSI package. For InstallShield 11.5 and earlier installations, Setup.exe launches a file called ISScript.msi that, in turn, installs the InstallScript engine that is required to run InstallScript code. For InstallShield 12 installations, Setup.exe launches a file called ISSetup.dll, which contains the InstallScript engine and executes the InstallScript code. The ISSetup.dll file is stored in the Binary table of the .msi file. 

More Info
For additional information about InstallScript Engine, read the article from Macrovision: Q108166
Repackaging an InstallScript MSI Setup to a Basic MSI Setup

Downloads
InstallScript Engine Version 7
InstallScript Engine Version 8
InstallScript Engine Version 9
InstallScript Engine Version 10
InstallScript Engine Version 10.5
InstallScript Engine Version 11

Download All Versions [Versions: 7,8,9,10,10.5,11,11.5; FileSize: 4.62 MB]: .ZIP | .RAR