How to add other languages to the TTS provided with win7？

Question

In fact, I want to c# write a code that can call the TTS function of win7 and make use of the voice library of win7.
This is part of my code:

namespace TTS1  
{  
    public partial class Form1 : Form  
    {  
        public Form1()  
        {  
            InitializeComponent();  
        }  

        List<SpObjectToken> Voices;  
         private void Form1_Load(object sender, EventArgs e)  
        {  
            var voice = new SpVoice();  
            Voices = voice.GetVoices().Cast<SpObjectToken>().ToList();  
            comboBox1.DataSource = Voices.Select(i => i.GetDescription()).ToList();  

        }  


        private void btnSpeak_Click(object sender, EventArgs e)                          
        {  

                var voice = new SpVoice  
                {  
                    Rate = 0,  
                    Volume = 100,  
                    Voice = Voices[comboBox1.SelectedIndex]  
                };  
                voice.Speak(textBox1.Text);  

Win7 Text to Speech function comes with Chinese and English speech synthesis by default.
How to import a speech package so that it can synthesize speech such as Japanese and Korean?
like this：

I tried to update the system, download the voice package and download the voice package online without success.
How do I realize this? Do you need other fix packs or updates?

Hope to get an answer, thank you