diff --git a/src/sys/ags.cpp b/src/sys/ags.cpp
index 108185d..2287219 100644
--- a/src/sys/ags.cpp
+++ b/src/sys/ags.cpp
@@ -386,16 +386,16 @@ AGS::~AGS()
 	// 退避領域の開放
 	for(int i = 0; i < 10; i++) {
 		if(menu_w[i].screen) {
-			free(menu_w[i].screen);
+			SDL_FreeSurface(menu_w[i].screen);
 		}
 		if(menu_w[i].window) {
-			free(menu_w[i].window);
+			SDL_FreeSurface(menu_w[i].window);
 		}
 		if(text_w[i].screen) {
-			free(text_w[i].screen);
+			SDL_FreeSurface(text_w[i].screen);
 		}
 		if(text_w[i].window) {
-			free(text_w[i].window);
+			SDL_FreeSurface(text_w[i].window);
 		}
 	}
 
diff --git a/src/sys/ags.h b/src/sys/ags.h
index 23fc90e..a12bf17 100644
--- a/src/sys/ags.h
+++ b/src/sys/ags.h
@@ -181,17 +181,13 @@ public:
 		int ey;
 		bool frame;
 		bool push;
-		uint8_t* screen;
+		SDL_Surface* screen;
 		int screen_x;
 		int screen_y;
-		int screen_width;
-		int screen_height;
 		Palette screen_palette;
-		uint8_t* window;
+		SDL_Surface* window;
 		int window_x;
 		int window_y;
-		int window_width;
-		int window_height;
 		Palette window_palette;
 	} WINDOW;
 	WINDOW menu_w[10];
diff --git a/src/sys/ags_window.cpp b/src/sys/ags_window.cpp
index 19ac3bd..6b21779 100644
--- a/src/sys/ags_window.cpp
+++ b/src/sys/ags_window.cpp
@@ -85,23 +85,17 @@ void AGS::open_text_window(int index, bool erase)
 	// 画面退避
 	if(text_w[index - 1].push) {
 		if(text_w[index - 1].screen) {
-			free(text_w[index - 1].screen);
+			SDL_FreeSurface(text_w[index - 1].screen);
 		}
 
-		text_w[index - 1].screen = (uint8_t*)malloc(width * height);
+		text_w[index - 1].screen = SDL_CreateRGBSurfaceWithFormat(0, width, height, 8, SDL_PIXELFORMAT_INDEX8);
+		SDL_SetSurfacePalette(text_w[index - 1].screen, hBmpScreen[0]->format->palette);
 		text_w[index - 1].screen_x = sx;
 		text_w[index - 1].screen_y = sy;
-		text_w[index - 1].screen_width = width;
-		text_w[index - 1].screen_height = height;
+		text_w[index - 1].screen_palette = screen_palette;
 
-		for(int y = 0; y < height && y + sy < 480; y++) {
-			uint32_t* scr = surface_line(hBmpDest, y + sy) + sx;
-			for(int x = 0; x < width && x + sx < 640; x++) {
-				uint8_t col = vram[0][y + sy][x + sx];
-				text_w[index - 1].screen_palette[col] = scr[x];
-				text_w[index - 1].screen[x + width * y] = col;
-			}
-		}
+		SDL_Rect rect = {sx, sy, width, height};
+		SDL_BlitSurface(hBmpScreen[0], &rect, text_w[index - 1].screen, NULL);
 	}
 
 	if(erase) {
@@ -111,14 +105,11 @@ void AGS::open_text_window(int index, bool erase)
 		// 窓復帰
 		sx = text_w[index - 1].window_x;
 		sy = text_w[index - 1].window_y;
-		width = text_w[index - 1].window_width;
-		height = text_w[index - 1].window_height;
+		width = text_w[index - 1].window->w;
+		height = text_w[index - 1].window->h;
 
-		for(int y = 0; y < height && y + sy < 480; y++) {
-			for(int x = 0; x < width && x + sx < 640; x++) {
-				vram[0][y + sy][x + sx] = text_w[index - 1].window[x + width * y];
-			}
-		}
+		SDL_Rect rect = {sx, sy, width, height};
+		SDL_BlitSurface(text_w[index - 1].window, NULL, hBmpScreen[0], &rect);
 
 		Palette palette = screen_palette;
 		screen_palette = text_w[index - 1].window_palette;
@@ -144,37 +135,28 @@ void AGS::close_text_window(int index, bool update)
 	// 窓退避
 	if(text_w[index - 1].push) {
 		if(text_w[index - 1].window) {
-			free(text_w[index - 1].window);
+			SDL_FreeSurface(text_w[index - 1].window);
 		}
 
-		text_w[index - 1].window = (uint8_t*)malloc(width * height);
+		text_w[index - 1].window = SDL_CreateRGBSurfaceWithFormat(0, width, height, 8, SDL_PIXELFORMAT_INDEX8);
+		SDL_SetSurfacePalette(text_w[index - 1].window, hBmpScreen[0]->format->palette);
 		text_w[index - 1].window_x = sx;
 		text_w[index - 1].window_y = sy;
-		text_w[index - 1].window_width = width;
-		text_w[index - 1].window_height = height;
+		text_w[index - 1].window_palette = screen_palette;
 
-		for(int y = 0; y < height && y + sy < 480; y++) {
-			uint32* scr = surface_line(hBmpDest, y + sy) + sx;
-			for(int x = 0; x < width && x + sx < 640; x++) {
-				uint8_t col = vram[0][y + sy][x + sx];
-				text_w[index - 1].window_palette[col] = scr[x];
-				text_w[index - 1].window[x + width * y] = col;
-			}
-		}
+		SDL_Rect rect = {sx, sy, width, height};
+		SDL_BlitSurface(hBmpScreen[0], &rect, text_w[index - 1].window, NULL);
 	}
 
 	// 画面復帰
 	if(text_w[index - 1].push && text_w[index - 1].screen) {
 		sx = text_w[index - 1].screen_x;
 		sy = text_w[index - 1].screen_y;
-		width = text_w[index - 1].screen_width;
-		height = text_w[index - 1].screen_height;
+		width = text_w[index - 1].screen->w;
+		height = text_w[index - 1].screen->h;
 
-		for(int y = 0; y < height && y + sy < 480; y++) {
-			for(int x = 0; x < width && x + sx < 640; x++) {
-				vram[0][y + sy][x + sx] = text_w[index - 1].screen[x + width * y];
-			}
-		}
+		SDL_Rect rect = {sx, sy, width, height};
+		SDL_BlitSurface(text_w[index - 1].screen, NULL, hBmpScreen[0], &rect);
 
 		Palette palette = screen_palette;
 		screen_palette = text_w[index - 1].screen_palette;
@@ -214,23 +196,17 @@ void AGS::open_menu_window(int index)
 	// 画面退避
 	if(menu_w[index - 1].push) {
 		if(menu_w[index - 1].screen) {
-			free(menu_w[index - 1].screen);
+			SDL_FreeSurface(menu_w[index - 1].screen);
 		}
 
-		menu_w[index - 1].screen = (uint8_t*)malloc(wwidth * wheight);
+		menu_w[index - 1].screen = SDL_CreateRGBSurfaceWithFormat(0, wwidth, wheight, 8, SDL_PIXELFORMAT_INDEX8);
+		SDL_SetSurfacePalette(menu_w[index - 1].screen, hBmpScreen[0]->format->palette);
 		menu_w[index - 1].screen_x = wsx;
 		menu_w[index - 1].screen_y = wsy;
-		menu_w[index - 1].screen_width = wwidth;
-		menu_w[index - 1].screen_height = wheight;
+		menu_w[index - 1].screen_palette = screen_palette;
 
-		for(int y = 0; y < wheight && y + wsy < 480; y++) {
-			uint32* scr = surface_line(hBmpDest, y + wsy) + wsx;
-			for(int x = 0; x < wwidth && x + wsx < 640; x++) {
-				uint8_t col = vram[0][y + wsy][x + wsx];
-				menu_w[index - 1].screen_palette[col] = scr[x];
-				menu_w[index - 1].screen[x + wwidth * y] = col;
-			}
-		}
+		SDL_Rect rect = {wsx, wsy, wwidth, wheight};
+		SDL_BlitSurface(hBmpScreen[0], &rect, menu_w[index - 1].screen, NULL);
 	}
 
 	// メニュー表示
@@ -268,14 +244,11 @@ void AGS::close_menu_window(int index)
 	if(menu_w[index - 1].push && menu_w[index - 1].screen) {
 		int sx = menu_w[index - 1].screen_x;
 		int sy = menu_w[index - 1].screen_y;
-		int width = menu_w[index - 1].screen_width;
-		int height = menu_w[index - 1].screen_height;
+		int width = menu_w[index - 1].screen->w;
+		int height = menu_w[index - 1].screen->h;
 
-		for(int y = 0; y < height && y + sy < 480; y++) {
-			for(int x = 0; x < width && x + sx < 640; x++) {
-				vram[0][y + sy][x + sx] = menu_w[index - 1].screen[x + width * y];
-			}
-		}
+		SDL_Rect rect = {sx, sy, width, height};
+		SDL_BlitSurface(menu_w[index - 1].screen, NULL, hBmpScreen[0], &rect);
 
 		Palette palette = screen_palette;
 		screen_palette = menu_w[index - 1].screen_palette;
diff --git a/src/sys/nact.cpp b/src/sys/nact.cpp
index 64a1b83..3c35e1d 100644
--- a/src/sys/nact.cpp
+++ b/src/sys/nact.cpp
@@ -585,11 +585,11 @@ bool NACT::load(int index)
 		fio->getw();
 
 		if (ags->menu_w[i].screen) {
-			free(ags->menu_w[i].screen);
+			SDL_FreeSurface(ags->menu_w[i].screen);
 		}
 		ags->menu_w[i].screen = NULL;
 		if (ags->menu_w[i].window) {
-			free(ags->menu_w[i].window);
+			SDL_FreeSurface(ags->menu_w[i].window);
 		}
 		ags->menu_w[i].window = NULL;
 	}
@@ -604,11 +604,11 @@ bool NACT::load(int index)
 		fio->getw();
 
 		if (ags->text_w[i].screen) {
-			free(ags->text_w[i].screen);
+			SDL_FreeSurface(ags->text_w[i].screen);
 		}
 		ags->text_w[i].screen = NULL;
 		if (ags->text_w[i].window) {
-			free(ags->text_w[i].window);
+			SDL_FreeSurface(ags->text_w[i].window);
 		}
 		ags->text_w[i].window = NULL;
 	}
diff --git a/src/sys/nact_sys2.cpp b/src/sys/nact_sys2.cpp
index 769b91c..a9c9d68 100644
--- a/src/sys/nact_sys2.cpp
+++ b/src/sys/nact_sys2.cpp
@@ -366,7 +366,7 @@ void NACT_Sys2::cmd_b()
 
 		// 退避画面の破棄
 		if(ags->menu_w[index - 1].screen) {
-			free(ags->menu_w[index - 1].screen);
+			SDL_FreeSurface(ags->menu_w[index - 1].screen);
 			ags->menu_w[index - 1].screen = NULL;
 		}
 		break;
@@ -389,12 +389,12 @@ void NACT_Sys2::cmd_b()
 
 		// 退避画面の破棄
 		if(ags->text_w[index - 1].screen) {
-			free(ags->text_w[index - 1].screen);
+			SDL_FreeSurface(ags->text_w[index - 1].screen);
 			ags->text_w[index - 1].screen = NULL;
 		}
 		// 退避窓の破棄
 		if(ags->text_w[index - 1].window) {
-			free(ags->text_w[index - 1].window);
+			SDL_FreeSurface(ags->text_w[index - 1].window);
 			ags->text_w[index - 1].window = NULL;
 		}
 		break;
diff --git a/src/sys/nact_sys3.cpp b/src/sys/nact_sys3.cpp
index 366c64c..8d47586 100644
--- a/src/sys/nact_sys3.cpp
+++ b/src/sys/nact_sys3.cpp
@@ -263,7 +263,7 @@ void NACT_Sys3::cmd_b()
 
 		// 退避画面の破棄
 		if(ags->menu_w[index - 1].screen) {
-			free(ags->menu_w[index - 1].screen);
+			SDL_FreeSurface(ags->menu_w[index - 1].screen);
 			ags->menu_w[index - 1].screen = NULL;
 		}
 		break;
@@ -280,12 +280,12 @@ void NACT_Sys3::cmd_b()
 
 		// 退避画面の破棄
 		if(ags->text_w[index - 1].screen) {
-			free(ags->text_w[index - 1].screen);
+			SDL_FreeSurface(ags->text_w[index - 1].screen);
 			ags->text_w[index - 1].screen = NULL;
 		}
 		// 退避窓の破棄
 		if(ags->text_w[index - 1].window) {
-			free(ags->text_w[index - 1].window);
+			SDL_FreeSurface(ags->text_w[index - 1].window);
 			ags->text_w[index - 1].window = NULL;
 		}
 		break;
@@ -295,7 +295,7 @@ void NACT_Sys3::cmd_b()
 			if (game_id.is(GameId::PROG_CD) && p4) {
 				// prostudent G オープニング画面化け対策
 				if(ags->text_w[index - 1].window) {
-					free(ags->text_w[index - 1].window);
+					SDL_FreeSurface(ags->text_w[index - 1].window);
 					ags->text_w[index - 1].window = NULL;
 				}
 			}