The ADE package includes the Custom StartupWizard to help you set the startup properties of the database just before you create a compiled version of the database. The startup properties determine how the database will display when the user opens it. For example, it controls whether the database window display or not. So, the Custom StartupWizard helps adjust the startup properties so that when a user opens your database, the display is presented exactly the way you want the user to see it.
So when do you use the Custom Startup Wizard? You use the wizard when you're ready to compile your database. Since your application has a really cool user interface with all the features your users will ever need, you only want the users to have access to what you developed for them.
Why do you need the Custom StartupWizard? There are really several reasons:
First of all, you've spent a lot of time developing your application. (You are calling your database an application by this point, aren't you? Microsoft Access Team may finally have acknowledged that Access developers do this—create applications rather than databases, that is. And, having heard our pain (needs), they created these tools for us.)
Your application has a really cool user interface that contains all of the tools you want your users to have and only the tools that you want them to have. You don't want users to be able to mass delete a bunch of data without your code having the opportunity to verify ...