For Each p As Process In System.Diagnostics.Process.GetProcessesByName( _
  "explorer")
    ' folgenden Methoden stehen dir zur Verfügung:
    'p.CloseMainWindow()
    'p.Kill()
Next

        Dim proc As New Process
        Dim si As New ProcessStartInfo("Notepad.exe", "C:\Text.txt")
        proc.StartInfo = si
        proc.Start()