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EDIT: Forget this - my mistake

How do I include in the bootstrapper the installation of a a programm, but not as a prerequisite?

I can add a programm to the custom Software Prerequisites tab to show up in the Setup.exe-bootstrapper, but it is always marked as being required, and when not checked then the "Next" button is deactivated.

(The "Force installation of this prerequisite" option on the Options tab when editing the prerequisite is not checked)

I just want to give it to the user as an option to install it.

EDIT:
Forget this - my mistake.
Though the "Next" button becomes inactive when the programm is unchecked, the "Finish" button can be clicked and the installation begins. So I guess this I didn't see what was happening