Private Sub lv_ItemCheck(ByVal sender As Object, ByVal e As _
      System.Windows.Forms.ItemCheckEventArgs) Handles lv.ItemCheck
        If e.NewValue = CheckState.Checked Then
            For Each lvi As ListViewItem In lv.CheckedItems
                lvi.Checked = False
            Next
        End If
    End Sub

Those people who think they know everything are a great annoyance to those of us who do - Isaac Asimov