Oh, sorry. I didn't notice you replied.

I'm not sure if I understand what you want to do. If I do understand correctly, then I'd have to suggest using other controls unless you really want a single visible tab. Anyway, I think the following code will do want you want.

Code:
    Protected Sub Page_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load

        TabPanel1.Visible = True
        TabPanel2.Visible = False
        TabPanel3.Visible = False
        TabPanel4.Visible = False
        TabPanel5.Visible = False

        TabContainer1.ActiveTabIndex = 0

    End Sub

    Protected Sub Button1_Click(ByVal sender As Object, ByVal e As EventArgs) Handles Button1.Click

        ' For some reason non-visible panel aren't
        ' part of the list so don't change ActiveTabIndex
        ' since the index of panel2 becomes 0

        TabPanel1.Visible = False
        TabPanel2.Visible = True

    End Sub