Index: src/settings.cpp
===================================================================
--- src/settings.cpp	(revision 13031)
+++ src/settings.cpp	(working copy)
@@ -1889,7 +1889,7 @@
 		Write_ValidateSetting(var, sd, (int32)p2);
 		if (sd->desc.proc != NULL) sd->desc.proc((int32)ReadValue(var, sd->save.conv));
 
-		InvalidateWindow(WC_GAME_OPTIONS, 0);
+		InvalidateWindow(WC_GAME_OPTIONS, GOWN_CONFIGUREPATCHES);
 	}
 
 	return CommandCost();
@@ -1918,7 +1918,7 @@
 			Write_ValidateSetting(var2, sd, value);
 		}
 		if (sd->desc.proc != NULL) sd->desc.proc((int32)ReadValue(var, sd->save.conv));
-		InvalidateWindow(WC_GAME_OPTIONS, 0);
+		InvalidateWindow(WC_GAME_OPTIONS, GOWN_CONFIGUREPATCHES);
 		return true;
 	}
 
Index: src/settings_gui.cpp
===================================================================
--- src/settings_gui.cpp	(revision 13031)
+++ src/settings_gui.cpp	(working copy)
@@ -290,7 +290,7 @@
 				case GAMEOPT_TOWNNAME_BTN: /* Town names */
 					if (_game_mode == GM_MENU) {
 						_opt_ptr->town_name = e->we.dropdown.index;
-						InvalidateWindow(WC_GAME_OPTIONS, 0);
+						InvalidateWindowClasses(WC_GAME_OPTIONS);
 					}
 					break;
 
@@ -340,7 +340,7 @@
 
 	if (flags & DC_EXEC) {
 		_opt_ptr->road_side = p1;
-		InvalidateWindow(WC_GAME_OPTIONS, 0);
+		InvalidateWindow(WC_GAME_OPTIONS, GOWN_GAMEOPTIONS);
 	}
 	return CommandCost();
 }
@@ -388,8 +388,8 @@
 
 void ShowGameOptions()
 {
-	DeleteWindowById(WC_GAME_OPTIONS, 0);
-	new Window(&_game_options_desc);
+	DeleteWindowByClass(WC_GAME_OPTIONS);
+	new Window(&_game_options_desc, NULL, GOWN_GAMEOPTIONS);
 }
 
 struct GameSettingData {
@@ -694,11 +694,11 @@
 
 void ShowGameDifficulty()
 {
-	DeleteWindowById(WC_GAME_OPTIONS, 0);
+	DeleteWindowByClass(WC_GAME_OPTIONS);
 	/* Copy current settings (ingame or in intro) to temporary holding place
 	 * change that when setting stuff, copy back on clicking 'OK' */
 	_opt_mod_temp = *_opt_ptr;
-	new Window(&_game_difficulty_desc);
+	new Window(&_game_difficulty_desc, NULL, GOWN_GAMEDIFFICULTY);
 }
 
 static const char *_patches_ui[] = {
@@ -1103,8 +1103,8 @@
 
 void ShowPatchesSelection()
 {
-	DeleteWindowById(WC_GAME_OPTIONS, 0);
-	new Window(&_patches_selection_desc);
+	DeleteWindowByClass(WC_GAME_OPTIONS);
+	new Window(&_patches_selection_desc, NULL, GOWN_CONFIGUREPATCHES);
 }
 
 
Index: src/misc_gui.cpp
===================================================================
--- src/misc_gui.cpp	(revision 13031)
+++ src/misc_gui.cpp	(working copy)
@@ -323,8 +323,8 @@
 
 void ShowAboutWindow()
 {
-	DeleteWindowById(WC_GAME_OPTIONS, 0);
-	new Window(&_about_desc);
+	DeleteWindowByClass(WC_GAME_OPTIONS);
+	new Window(&_about_desc, NULL, GOWN_ABOUT);
 }
 
 static uint64 _errmsg_decode_params[20];
Index: src/newgrf_gui.cpp
===================================================================
--- src/newgrf_gui.cpp	(revision 13031)
+++ src/newgrf_gui.cpp	(working copy)
@@ -211,7 +211,7 @@
 						*list = c;
 
 						DeleteWindowByClass(WC_SAVELOAD);
-						InvalidateWindowData(WC_GAME_OPTIONS, 0);
+						InvalidateWindowData(WC_GAME_OPTIONS, GOWN_NEWGRFMANAGE);
 					}
 					break;
 
@@ -583,7 +583,7 @@
 	Window *w;
 
 	DeleteWindowByClass(WC_GAME_OPTIONS);
-	w = new Window(&_newgrf_desc);
+	w = new Window(&_newgrf_desc, NULL, GOWN_NEWGRFMANAGE);
 	if (w == NULL) return;
 
 	w->resize.step_height = 14;
Index: src/window_type.h
===================================================================
--- src/window_type.h	(revision 13031)
+++ src/window_type.h	(working copy)
@@ -71,7 +71,7 @@
 	WC_SEND_NETWORK_MSG,
 	WC_DROPDOWN_MENU,
 	WC_BUILD_INDUSTRY,
-	WC_GAME_OPTIONS,
+	WC_GAME_OPTIONS,             ///< Game options. @see GameOptionsWindowNumber
 	WC_NETWORK_WINDOW,
 	WC_INDUSTRY_DIRECTORY,
 	WC_MESSAGE_HISTORY,
@@ -100,6 +100,17 @@
 struct WindowEvent;
 typedef int32 WindowNumber;
 
+/** Unique WindowNumber for each of the WC_GAME_OPTIONS windows */
+enum GameOptionsWindowNumber {
+	GOWN_GAMEOPTIONS,      ///< Window number for the 'game options' window
+	GOWN_GAMEDIFFICULTY,   ///< Window number for the 'game difficulty' window
+	GOWN_CONFIGUREPATCHES, ///< Window number for the 'configure patches' window
+	GOWN_ABOUT,            ///< Window number for the 'about' window
+	GOWN_NEWSOPTIONS,      ///< Window number for the 'news settings' window
+	GOWN_NEWGRFMANAGE      ///< Window number for the 'manage NewGRF' window
+};
+
+
 /**
  * You cannot 100% reliably calculate the biggest custom struct as
  * the number of pointers in it and alignment will have a huge impact.
Index: src/rail_gui.cpp
===================================================================
--- src/rail_gui.cpp	(revision 13031)
+++ src/rail_gui.cpp	(working copy)
@@ -1328,14 +1328,14 @@
 				case BSW_DRAG_SIGNALS_DENSITY_DECREASE:
 					if (_patches.drag_signals_density > 1) {
 						_patches.drag_signals_density--;
-						SetWindowDirty(FindWindowById(WC_GAME_OPTIONS, 0));
+						InvalidateWindow(WC_GAME_OPTIONS, GOWN_CONFIGUREPATCHES);
 					}
 					break;
 
 				case BSW_DRAG_SIGNALS_DENSITY_INCREASE:
 					if (_patches.drag_signals_density < 20) {
 						_patches.drag_signals_density++;
-						SetWindowDirty(FindWindowById(WC_GAME_OPTIONS, 0));
+						InvalidateWindow(WC_GAME_OPTIONS, GOWN_CONFIGUREPATCHES);
 					}
 					break;
 
Index: src/news_gui.cpp
===================================================================
--- src/news_gui.cpp	(revision 13031)
+++ src/news_gui.cpp	(working copy)
@@ -930,8 +930,8 @@
 
 void ShowMessageOptions()
 {
-	DeleteWindowById(WC_GAME_OPTIONS, 0);
-	new Window(&_message_options_desc);
+	DeleteWindowByClass(WC_GAME_OPTIONS);
+	new Window(&_message_options_desc, NULL, GOWN_NEWSOPTIONS);
 }
 
 
Index: src/players.cpp
===================================================================
--- src/players.cpp	(revision 13031)
+++ src/players.cpp	(working copy)
@@ -68,7 +68,7 @@
 		_patches.autorenew        = p->engine_renew;
 		_patches.autorenew_months = p->engine_renew_months;
 		_patches.autorenew_money  = p->engine_renew_money;
-		InvalidateWindow(WC_GAME_OPTIONS, 0);
+		InvalidateWindow(WC_GAME_OPTIONS, GOWN_CONFIGUREPATCHES);
 	}
 }
 
@@ -693,7 +693,7 @@
 				p->engine_renew = HasBit(p2, 0);
 				if (IsLocalPlayer()) {
 					_patches.autorenew = p->engine_renew;
-					InvalidateWindow(WC_GAME_OPTIONS, 0);
+					InvalidateWindow(WC_GAME_OPTIONS, GOWN_CONFIGUREPATCHES);
 				}
 			}
 			break;
@@ -706,7 +706,7 @@
 				p->engine_renew_months = (int16)p2;
 				if (IsLocalPlayer()) {
 					_patches.autorenew_months = p->engine_renew_months;
-					InvalidateWindow(WC_GAME_OPTIONS, 0);
+					InvalidateWindow(WC_GAME_OPTIONS, GOWN_CONFIGUREPATCHES);
 				}
 			}
 			break;
@@ -719,7 +719,7 @@
 				p->engine_renew_money = p2;
 				if (IsLocalPlayer()) {
 					_patches.autorenew_money = p->engine_renew_money;
-					InvalidateWindow(WC_GAME_OPTIONS, 0);
+					InvalidateWindow(WC_GAME_OPTIONS, GOWN_CONFIGUREPATCHES);
 				}
 			}
 			break;
@@ -771,7 +771,7 @@
 					_patches.autorenew = p->engine_renew;
 					_patches.autorenew_months = p->engine_renew_months;
 					_patches.autorenew_money = p->engine_renew_money;
-					InvalidateWindow(WC_GAME_OPTIONS, 0);
+					InvalidateWindow(WC_GAME_OPTIONS, GOWN_CONFIGUREPATCHES);
 				}
 			}
 			break;
Index: src/misc_cmd.cpp
===================================================================
--- src/misc_cmd.cpp	(revision 13031)
+++ src/misc_cmd.cpp	(working copy)
@@ -405,7 +405,7 @@
 		/* If we are a network-client, update the difficult setting (if it is open).
 		 * Use this instead of just dirtying the window because we need to load in
 		 * the new difficulty settings */
-		if (_networking && !_network_server && FindWindowById(WC_GAME_OPTIONS, 0) != NULL) {
+		if (_networking && !_network_server && FindWindowById(WC_GAME_OPTIONS, GOWN_GAMEDIFFICULTY) != NULL) {
 			ShowGameDifficulty();
 		}
 	}