Imports System.Data.OleDb
Public Class Form2
    Private conn As OleDbConnection
...

    Private Sub Form2_Load(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles MyBase.Load
        conn = New OleDbConnection("Provider=Microsoft.Jet.OLEDB.4.0; Data" & _
        "Source=C:\testdb.mdb;")
    End Sub

    Private Sub btn_speichern_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles btn_speichern.Click
        If txt_name.Text <> "" Then
            If txt_benutzer.Text = "" Then txt_benutzer.Text = " "
            If txt_taktfrequenz.Text = "" Then txt_taktfrequenz.Text = 0
            If txt_arbeitsspeicher.Text = "" Then txt_arbeitsspeicher.Text = 0
            If txt_betriebssystem.Text = "" Then txt_betriebssystem.Text = " "
            Dim sql As String = "INSERT INTO Rechner(Name, Benutzer," & _
              "Taktfrequenz, Arbeitsspeicher, Betriebssystem) VALUES ('" & _
              txt_name.Text & "', '" & txt_benutzer.Text & "', '" & _
              txt_taktfrequenz.Text & "', '" & txt_arbeitsspeicher.Text & "'," & _
              "'" & txt_betriebssystem.Text & "')"
            Dim cmd As New OleDbCommand(sql, conn)
            Try
                conn.Open()
                cmd.ExecuteNonQuery()
            Catch ex As Exception
                MsgBox(ex.Message)
            End Try
            conn.Close()
            Me.Close()
        Else
            MsgBox("Es muss mindestens der Name des Rechners eingegeben" & _
              "werden!", MsgBoxStyle.Exclamation, "Lizenzverwaltung")
        End If
    End Sub