Let us start here, from square one. No, from Zero!

cfg/configurator_wnd.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <windows.h>
+
+namespace cfg {
+
+    class ConfiguratorWindow {
+    public:
+
+        HWND hWnd;
+
+        ConfiguratorWindow();
+        ~ConfiguratorWindow();
+
+        void run();
+
+        static LRESULT CALLBACK window_proc(HWND hwnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
+    };
+}