diff --git a/Source/diablo.cpp b/Source/diablo.cpp
index ccdc90a0f..e2a757fad 100644
--- a/Source/diablo.cpp
+++ b/Source/diablo.cpp
@@ -564,7 +564,7 @@ static void GetMousePos(LPARAM lParam)
 	MouseY = (short)((lParam >> 16) & 0xffff);
 }
 
-LRESULT DisableInputWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
+void DisableInputWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 {
 	switch (uMsg) {
 	case DVL_WM_KEYDOWN:
@@ -574,71 +574,71 @@ LRESULT DisableInputWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 	case DVL_WM_SYSCOMMAND:
 	case DVL_WM_MOUSEMOVE:
 		GetMousePos(lParam);
-		return 0;
+		return;
 	case DVL_WM_LBUTTONDOWN:
 		if (sgbMouseDown != 0)
-			return 0;
+			return;
 		sgbMouseDown = 1;
-		return 0;
+		return;
 	case DVL_WM_LBUTTONUP:
 		if (sgbMouseDown != 1)
-			return 0;
+			return;
 		sgbMouseDown = 0;
-		return 0;
+		return;
 	case DVL_WM_RBUTTONDOWN:
 		if (sgbMouseDown != 0)
-			return 0;
+			return;
 		sgbMouseDown = 2;
-		return 0;
+		return;
 	case DVL_WM_RBUTTONUP:
 		if (sgbMouseDown != 2)
-			return 0;
+			return;
 		sgbMouseDown = 0;
-		return 0;
+		return;
 	case DVL_WM_CAPTURECHANGED:
 		if (hWnd == (HWND)lParam)
-			return 0;
+			return;
 		sgbMouseDown = 0;
-		return 0;
+		return;
 	}
 
-	return MainWndProc(hWnd, uMsg, wParam, lParam);
+	MainWndProc(hWnd, uMsg, wParam, lParam);
 }
 
-LRESULT GM_Game(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
+void GM_Game(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 {
 	switch (uMsg) {
 	case DVL_WM_KEYDOWN:
 		PressKey(wParam);
-		return 0;
+		return;
 	case DVL_WM_KEYUP:
 		ReleaseKey(wParam);
-		return 0;
+		return;
 	case DVL_WM_CHAR:
 		PressChar(wParam);
-		return 0;
+		return;
 	case DVL_WM_SYSKEYDOWN:
 		if (PressSysKey(wParam))
-			return 0;
+			return;
 		break;
 	case DVL_WM_SYSCOMMAND:
 		if (wParam == DVL_SC_CLOSE) {
 			gbRunGame = FALSE;
 			gbRunGameResult = FALSE;
-			return 0;
+			return;
 		}
 		break;
 	case DVL_WM_MOUSEMOVE:
 		GetMousePos(lParam);
 		gmenu_on_mouse_move();
-		return 0;
+		return;
 	case DVL_WM_LBUTTONDOWN:
 		GetMousePos(lParam);
 		if (sgbMouseDown == 0) {
 			sgbMouseDown = 1;
 			track_repeat_walk(LeftMouseDown(wParam));
 		}
-		return 0;
+		return;
 	case DVL_WM_LBUTTONUP:
 		GetMousePos(lParam);
 		if (sgbMouseDown == 1) {
@@ -646,20 +646,20 @@ LRESULT GM_Game(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 			LeftMouseUp();
 			track_repeat_walk(FALSE);
 		}
-		return 0;
+		return;
 	case DVL_WM_RBUTTONDOWN:
 		GetMousePos(lParam);
 		if (sgbMouseDown == 0) {
 			sgbMouseDown = 2;
 			RightMouseDown();
 		}
-		return 0;
+		return;
 	case DVL_WM_RBUTTONUP:
 		GetMousePos(lParam);
 		if (sgbMouseDown == 2) {
 			sgbMouseDown = 0;
 		}
-		return 0;
+		return;
 	case DVL_WM_CAPTURECHANGED:
 		if (hWnd != (HWND)lParam) {
 			sgbMouseDown = 0;
@@ -689,10 +689,10 @@ LRESULT GM_Game(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam)
 			PaletteFadeIn(8);
 		nthread_ignore_mutex(FALSE);
 		gbGameLoopStartup = TRUE;
-		return 0;
+		return;
 	}
 
-	return MainWndProc(hWnd, uMsg, wParam, lParam);
+	MainWndProc(hWnd, uMsg, wParam, lParam);
 }
 
 BOOL LeftMouseDown(int wParam)
diff --git a/Source/diablo.h b/Source/diablo.h
index c320d49a5..5910be0c9 100644
--- a/Source/diablo.h
+++ b/Source/diablo.h
@@ -76,8 +76,8 @@ void diablo_init_screen();
 void diablo_reload_process(HINSTANCE hInstance);
 void diablo_quit(int exitStatus);
 BOOL PressEscKey();
-LRESULT DisableInputWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
-LRESULT GM_Game(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
+void DisableInputWndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
+void GM_Game(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
 BOOL LeftMouseDown(int wParam);
 BOOL LeftMouseCmd(BOOL bShift);
 BOOL TryIconCurs();
diff --git a/Source/init.cpp b/Source/init.cpp
index 520ad23e7..3052e6abc 100644
--- a/Source/init.cpp
+++ b/Source/init.cpp
@@ -171,7 +171,7 @@ void init_get_file_info()
 	snprintf(gszVersionNumber, sizeof(gszVersionNumber) / sizeof(char), "version %s", PROJECT_VERSION);
 }
 
-LRESULT MainWndProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
+void MainWndProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
 {
 	switch (Msg) {
 	case DVL_WM_ERASEBKGND:
diff --git a/Source/init.h b/Source/init.h
index 1790f7dbf..a96537cfa 100644
--- a/Source/init.h
+++ b/Source/init.h
@@ -35,7 +35,7 @@ void init_disable_screensaver(BOOLEAN disable);
 void init_create_window();
 void init_archives();
 void init_get_file_info();
-LRESULT MainWndProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam);
+void MainWndProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam);
 void init_activate_window(HWND hWnd, BOOL bActive);
 WNDPROC SetWindowProc(WNDPROC NewProc);
 
diff --git a/Source/movie.h b/Source/movie.h
index 5927a3226..69eb7f718 100644
--- a/Source/movie.h
+++ b/Source/movie.h
@@ -16,7 +16,7 @@ extern BYTE movie_playing;
 extern BOOL loop_movie;
 
 void play_movie(const char *pszMovie, BOOL user_can_close);
-LRESULT MovieWndProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam);
+void MovieWndProc(HWND hWnd, UINT Msg, WPARAM wParam, LPARAM lParam);
 
 /* rdata */
 
diff --git a/SourceS/miniwin/misc.h b/SourceS/miniwin/misc.h
index 17886c62e..b100a0b3f 100644
--- a/SourceS/miniwin/misc.h
+++ b/SourceS/miniwin/misc.h
@@ -18,9 +18,8 @@ typedef void *PVOID;
 
 typedef unsigned int UINT;
 
-typedef uintptr_t WPARAM;
-typedef uintptr_t LPARAM;
-typedef uintptr_t LRESULT;
+typedef int32_t WPARAM;
+typedef int32_t LPARAM;
 
 //
 // Handles
@@ -29,7 +28,7 @@ typedef void *HANDLE;
 
 typedef HANDLE HWND, HMODULE, HDC, HINSTANCE;
 
-typedef LRESULT(*WNDPROC)(HWND, UINT, WPARAM, LPARAM);
+typedef void(*WNDPROC)(HWND, UINT, WPARAM, LPARAM);
 
 typedef struct _FILETIME {
 	DWORD dwLowDateTime;
@@ -54,7 +53,7 @@ SHORT GetAsyncKeyState(int vKey);
 bool PeekMessage(LPMSG lpMsg);
 
 bool TranslateMessage(const MSG *lpMsg);
-LRESULT DispatchMessage(const MSG *lpMsg);
+void DispatchMessage(const MSG *lpMsg);
 bool PostMessage(UINT Msg, WPARAM wParam, LPARAM lParam);
 
 #ifndef TRUE
diff --git a/SourceX/miniwin/misc_msg.cpp b/SourceX/miniwin/misc_msg.cpp
index 82f1be26b..6036733ce 100644
--- a/SourceX/miniwin/misc_msg.cpp
+++ b/SourceX/miniwin/misc_msg.cpp
@@ -708,11 +708,11 @@ SHORT GetAsyncKeyState(int vKey)
 	}
 }
 
-LRESULT DispatchMessage(const MSG *lpMsg)
+void DispatchMessage(const MSG *lpMsg)
 {
 	assert(CurrentProc);
 
-	return CurrentProc(NULL, lpMsg->message, lpMsg->wParam, lpMsg->lParam);
+	CurrentProc(NULL, lpMsg->message, lpMsg->wParam, lpMsg->lParam);
 }
 
 bool PostMessage(UINT Msg, WPARAM wParam, LPARAM lParam)