Main function of window application [STAThread] static void Main() { if (SingleInstanceCode.SingleInstanceClass.CheckForOtherApp("{2D484E4F-9080-4D30-B12C-87405DD609AC}"))//Unique key { MessageBox.Show("Application is already running.", "Information", MessageBoxButtons.OK, MessageBoxIcon.Information); return; } Application.EnableVisualStyles(); Application.SetCompatibleTextRenderingDefault(false); Application.Run(new Form1()); } SingleInstCode Class using System; using System.Collections.Generic; using System.Windows.Form...