Napisałem do tego klasę pomocnika. Pokazuje okno dialogowe logowania „XP Style”, a nie to, które pokazałeś na zrzucie ekranu, ale będziesz mógł przejść od tego miejsca, aby wyświetlić także „nowe” okno dialogowe:

public static class UserHelper
{
    [Flags]
    public enum CREDUI_FLAGS
    {
        INCORRECT_PASSWORD = 0x1,
        DO_NOT_PERSIST = 0x2,
        REQUEST_ADMINISTRATOR = 0x4,
        EXCLUDE_CERTIFICATES = 0x8,
        REQUIRE_CERTIFICATE = 0x10,
        SHOW_SAVE_CHECK_BOX = 0x40,
        ALWAYS_SHOW_UI = 0x80,
        REQUIRE_SMARTCARD = 0x100,
        PASSWORD_ONLY_OK = 0x200,
        VALIDATE_USERNAME = 0x400,
        COMPLETE_USERNAME = 0x800,
        PERSIST = 0x1000,
        SERVER_CREDENTIAL = 0x4000,
        EXPECT_CONFIRMATION = 0x20000,
        GENERIC_CREDENTIALS = 0x40000,
        USERNAME_TARGET_CREDENTIALS = 0x80000,
        KEEP_USERNAME = 0x100000,
    }


    public enum CredUIReturnCodes
    {
        NO_ERROR = 0,
        ERROR_CANCELLED = 1223,
        ERROR_NO_SUCH_LOGON_SESSION = 1312,
        ERROR_NOT_FOUND = 1168,
        ERROR_INVALID_ACCOUNT_NAME = 1315,
        ERROR_INSUFFICIENT_BUFFER = 122,
        ERROR_INVALID_PARAMETER = 87,
        ERROR_INVALID_FLAGS = 1004,
        ERROR_BAD_ARGUMENTS = 160
    }


    [StructLayout(LayoutKind.Sequential, CharSet = CharSet.Unicode)]
    public struct CREDUI_INFO
    {
        public int cbSize;
        public IntPtr hwndParent;
        public string pszMessageText;
        public string pszCaptionText;
        public IntPtr hbmBanner;
    }


    [DllImport("credui", EntryPoint = "CredUIPromptForCredentialsW", CharSet = CharSet.Unicode)]
    private static extern CredUIReturnCodes CredUIPromptForCredentials(ref CREDUI_INFO creditUR, string targetName, IntPtr reserved1, int iError, StringBuilder userName, int maxUserName, StringBuilder password, int maxPassword, [MarshalAs(UnmanagedType.Bool)] ref bool pfSave, CREDUI_FLAGS flags);

    [DllImport("credui", EntryPoint = "CredUIParseUserNameW", CharSet = CharSet.Unicode)]
    private static extern CredUIReturnCodes CredUIParseUserName(string userName, StringBuilder user, int userMaxChars, StringBuilder domain, int domainMaxChars);

    const int MAX_USER_NAME = 100;
    const int MAX_PASSWORD = 100;
    const int MAX_DOMAIN = 100;

    public static CredUIReturnCodes PromptForCredentials(System.Windows.Window parentWindow, ref CREDUI_INFO creditUI, string targetName, int netError, out string domainName, out string userName, out string password, ref bool save, CREDUI_FLAGS flags)
    {
        userName = String.Empty;
        domainName = String.Empty;
        password = String.Empty;

        creditUI.cbSize = Marshal.SizeOf(creditUI);
        creditUI.hwndParent = new WindowInteropHelper(parentWindow).Handle;

        StringBuilder user = new StringBuilder(MAX_USER_NAME);
        StringBuilder pwd = new StringBuilder(MAX_PASSWORD);
        CredUIReturnCodes result = CredUIPromptForCredentials(ref creditUI, targetName, IntPtr.Zero, netError, user, MAX_USER_NAME, pwd, MAX_PASSWORD, ref save, flags);
        if (result == CredUIReturnCodes.NO_ERROR)
        {
            string tempUserName = user.ToString();
            string tempPassword = pwd.ToString();

            StringBuilder userBuilder = new StringBuilder();
            StringBuilder domainBuilder = new StringBuilder();

            CredUIReturnCodes returnCode = CredUIParseUserName(tempUserName, userBuilder, int.MaxValue, domainBuilder, int.MaxValue);
            switch (returnCode)
            {
                case CredUIReturnCodes.NO_ERROR:
                    userName = userBuilder.ToString();
                    domainName = domainBuilder.ToString();
                    password = tempPassword;
                    return returnCode;

                case CredUIReturnCodes.ERROR_INVALID_ACCOUNT_NAME:
                    userName = tempUserName;
                    domainName = String.Empty;
                    password = tempPassword;
                    return returnCode;

                default:
                    return returnCode;
            }
        }

        return result;
    }
}

Przywołuję to za pomocą:

UserHelper.CREDUI_INFO info = new UserHelper.CREDUI_INFO();
info.pszCaptionText = host;
info.pszMessageText = "Please log in:";

UserHelper.CREDUI_FLAGS flags = UserHelper.CREDUI_FLAGS.GENERIC_CREDENTIALS |
                                UserHelper.CREDUI_FLAGS.ALWAYS_SHOW_UI |
                                UserHelper.CREDUI_FLAGS.DO_NOT_PERSIST |                                               
                                UserHelper.CREDUI_FLAGS.VALIDATE_USERNAME |
                                UserHelper.CREDUI_FLAGS.INCORRECT_PASSWORD;

UserHelper.CredUIReturnCodes result = UserHelper.PromptForCredentials(this, ref info, host, 0, out domainName, out userName, out password, ref saveSettings, flags);