Private Const filename As String = "c:\sample.xml"

    Private Sub insertData(ByVal number As Integer, ByVal count As Integer)
        Dim doc As XmlDocument = New XmlDocument
        doc.Load(filename)
        For i As Integer = 0 To count - 1
            Dim newElement As XmlElement = doc.CreateElement("data")
            newElement.InnerText = "Number " + (number + i).ToString()
            doc.DocumentElement.InsertBefore(newElement, doc.DocumentElement.FirstChild)
        Next

        Dim tempFullPath As String = Path.ChangeExtension(filename, ".$$$")
        Dim bakFullPath As String = Path.ChangeExtension(filename, ".bak")

        doc.Save(tempFullPath)
        If File.Exists(filename) Then
            File.Delete(bakFullPath)
            File.Move(filename, bakFullPath)
        End If
        File.Move(tempFullPath, filename)
    End Sub

    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        insertData(0, 1000)
    End Sub