Display registry value

I am trying to display the value of DefaultPassword from HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon but when ever I try I keep getting "Object reference not set to an instance of an object."  If I change the string value I am trying to get information from to Shell within the same key it works fine.  Can anyone explain why one works and the other doesn't?  I have verified that DefaultPassword is in my registry and I have given it a value or password.

        private void Form1_Load(object sender, EventArgs e)
        {
            try
            {
                loadReg();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message.ToString());
            }
        }

        void loadReg()
        {
            Key = Registry.LocalMachine.OpenSubKey(@"SOFTWARE\Microsoft\Windows NT\CurrentVersion\Winlogon", true);

            string Val;     
            //Doesn't work
            Val = Key.GetValue("DefaultPassword").ToString();
            
            //Works
            //Val = Key.GetValue("Shell").ToString();
            textBox1.Text = Val;
        }

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Thanks,

Dustin