Use this code to make sure that users can only launch one instance of an application.
static void Main() { Process ThisProcess = Process.GetCurrentProcess(); Process [] AllProcesses = Process.GetProcessesByName(ThisProcess.ProcessName); if (AllProcesses.Length > 1) { MessageBox.Show(ThisProcess.ProcessName + " is already running",ThisProcess.ProcessName, MessageBoxButtons.OK, MessageBoxIcon.Error); } else { Application.Run(new MainForm()); }}