HOW TO change the StartPage of the Windows Phone 7 Application in Visual Studio 2010 [VB.NET]

Expand the My Project folder into Solution Explorer of the Visual Basic Windows Phone Application Project and Open the WMAppManifest.xml file.
Change the NavigationPage with you new StartPage filename (case sensitive).

    <Tasks>
      <DefaultTask  Name ="_default" NavigationPage="MainPage.xaml"/>
    </Tasks>

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