KeyGen.cs

using System;
using System.Reflection;
using System.IO;

namespace StKeyGen
{
    class Program
    {
        static void Main(string[] args)
        {
            Type keygen = null;

            try
            {
                keygen = Assembly.LoadFile(Directory.GetCurrentDirectory() + @"\St.exe").GetType("St.KeyGeneratorLib");
            }
            catch {
                Console.WriteLine("Error!");
                Console.ReadLine();
                Environment.Exit(1);
            }

            if (keygen != null)
            {
                String pid = (String)keygen.GetMethod("GeneraIDProdotto").Invoke(null, null);
                String mod = (String)keygen.GetMethod("modificaIDProdotto").Invoke(null, new object[] { pid });
                String reg = (String)keygen.GetMethod("GeneraIDRegistrazione").Invoke(null, new object[] { mod });
                
                Console.WriteLine(reg);
            }
            else {
                Console.WriteLine("Error!");
            }

            Console.ReadLine();
        }
    }
}

Long.reg

Windows Registry Editor Version 5.00

[HKEY_CURRENT_USER\Software\VB and VBA Program Settings\Application\S]
"AR"="10000"
"IsFiSt"="False"