im wanting to make my program have to enter a serial and you dont have to enter anymore (Only once) if you want the full version, i have some code here, but i cant seem to get it to work properly, Can anyone help me? this is the last piece i have to do and its finished.

Code:
Private Sub KryptonButton1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles KryptonButton1.Click
        If KryptonTextBox1.Text = "" Then
            MsgBox("Whoops! - Please make sure that all of the information with the * is filled out, and then try again!", MsgBoxStyle.Critical, "Whoops!")

        Else
          
                If KryptonTextBox1.Text = "N5869-N2201-N4859-N7832" Then
                    MsgBox("Thank you for registering, enjoy the full program! Noter will now restart to apply all changes!", MsgBoxStyle.Information, "Thank you!")
                    Form2.OptionsToolStripMenuItem.Enabled = True




                    Dim objStreamWriter As StreamWriter

                    'Pass the file path and the file name to the StreamWriter constructor.
                objStreamWriter = New StreamWriter("C:\NoterPRO.txt")

                    'Write a line of text. 
                objStreamWriter.WriteLine("Serial encrypted")

                    'Close the file.
                    objStreamWriter.Close()



                objStreamWriter.Close()
                Dim retval As String
                retval = Dir$("c:\NoterPRO.txt")
                If retval = "Serial.txt" Then
                Form2.OptionsToolStripMenuItem.Enabled = True
                KryptonTextBox1.Text = "You have already registerd Noter!"
                KryptonTextBox1.Enabled = False
                    KryptonButton1.Enabled = False
                    Application.Restart()
            End If
        End If
            End If
    End Sub
Code:
Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        Dim retval As String
        retval = Dir$("c:\NoterPRO.txt")
        If retval = "Serial.txt" Then
            OptionsToolStripMenuItem.Enabled = True
            Form3.KryptonTextBox1.Text = "You have already registerd Noter!"
            Form3.KryptonTextBox1.Enabled = False
            Form3.KryptonButton1.Enabled = False
        End If
    End Sub