Program.cs

using System;
using System.Windows.Forms;

namespace ChatBotApp
{
    internal static class Program
    {
        
        [STAThread]
        static void Main()
        {
            Application.EnableVisualStyles();
            Application.SetCompatibleTextRenderingDefault(false);
            
            // Check if another instance is already running
            bool createdNew;
            using (var mutex = new System.Threading.Mutex(true, "RathiChatBot2", out createdNew))
            {
                if (!createdNew)
                {
                    MessageBox.Show("Rathi ChatBot 2.0 is already running!", "Rathi ChatBot 2.0", 
                        MessageBoxButtons.OK, MessageBoxIcon.Information);
                    return;
                }

                Application.Run(new MainForm());
            }
        }
    }
}