Another approach is to use the UI Automation technology that's built in Windows. For example, this sample Console app should work. And because it's event-based, it does not need to use timers which can be context-dependent:

public static void Main(string[] args)
{
    Automation.AddAutomationEventHandler(WindowPattern.WindowOpenedEvent, AutomationElement.RootElement, TreeScope.Children, (sender, e) =>
    {
        var element = sender as AutomationElement;
        if (element.Current.Name == "Параметры быстродействия")
        {
            Console.WriteLine("hwnd:" + element.Current.NativeWindowHandle);
        }
    });

    Process.Start("SystemPropertiesPerformance.exe");
    Console.ReadLine(); // wait ...
    Automation.RemoveAllEventHandlers(); // cleanup
}

It works fine on my Windows 10 x64 machine. If this doesn't work, make sure your program and SystemPropertiesPerformance.exe run at the same UAC level.