OK this should answer your question.:)
Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
MenuStrip2.Hide()
End Sub
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
MenuStrip2.Show()
MenuStrip1.Hide()
End Sub
OK so I have two menustrips, now when the form loads the second one is hidden and the first one is shown then if the button(in your case if your logged in) is clicked then show menustrip2 and hide menustrip1.
A man can be defined by what he does when no one is looking.
Science is only an educated theory, which we cannot disprove.