C# execute system command doesn't work correctly

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C#

system

hello friends.
i have a windows form and want to when a program start, Explorer.exe disable and when user click on specific button, explorer.exe starts and show taskbar and start menu correctly.
here is my problem: when my program starts working, explorer.exe disable correctly and there is no problem.but when i click button1, just "My Document" window appear and taskbar and start menu are invisible. note that when i start explorer.exe by cmd there is not any problem and taskbar and start menu become visible, but when i execute same command by c#, just my document window appear.
here is my code:

  public Form1()
        {
            InitializeComponent();
            System.Diagnostics.Process process = new System.Diagnostics.Process();
            System.Diagnostics.ProcessStartInfo startInfo = new    System.Diagnostics.ProcessStartInfo();
            startInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
            startInfo.FileName = "cmd.exe";
            startInfo.Arguments = "/C Taskkill /IM explorer.exe /F";//command for kill explorer.exe process
            process.StartInfo = startInfo;
            process.Start();

        }

private void button1_Click(object sender, EventArgs e)
        {
            System.Diagnostics.Process process = new System.Diagnostics.Process();
            System.Diagnostics.ProcessStartInfo startInfo = new System.Diagnostics.ProcessStartInfo();
            startInfo.WindowStyle = System.Diagnostics.ProcessWindowStyle.Hidden;
            startInfo.FileName = "cmd.exe";
            startInfo.Arguments = "/C explorer.exe /F";//command for start explorer.exe
            process.StartInfo = startInfo;
            process.Start();

        }

please someone help me.
thanks in advance.