How to: Choose the Startup Form in a Windows Application
When you add a Windows Form to a project, it will not display itself by default at run time. For information about how to show a form at run time, see Displaying Modal and Modeless Windows Forms. However, the form created when you choose a Windows application from the New Project dialog box will be the startup form by default. To change the startup form, use the Project property page.
To set the startup form in Windows Forms
In Solution Explorer, right-click the project and choose Properties.
The Project property page opens with the Application properties displayed.
Choose the form you want as the startup form from the Startup Object drop-down list.