We have an application which we licence to separate companies. The app is customised to fit their brand; basically it is the same app but with a different theme file. We generate separate installers for each vendor as each app requires different configurations (servers to connect to, updates etc).

So each installer contains the same compiled application but with different configurations. All of this is managed by our build system so adding a new vendor is just a matter of creating a new theme and a simple include script for Inno Setup.

Our problem is that we want to ensure that when a user installs the app from vendor A they will not be able to install it from vendor B unless they explicitly uninstall the existing app.

Is there some setting in Inno Setup which will check if there is an existing installation (either from the same vendor or a different one) and tell the user they have to remove the existing installation?