is it possible to use windows application as a custom action for setup project? All the custom action examples i have seen so far were class library applications. i wonder if windows application is also possible?

Do you mean you want to write your own setup application or did I misunderstood your question?

there is an option to specify custom action for your msi project. there you can specify class library project for your custom action project. i tried using windows application project as custom action project but it didnt work.