diff --git a/LEGO1/omni/include/mxmusicmanager.h b/LEGO1/omni/include/mxmusicmanager.h
index 6deb88b3..7470c640 100644
--- a/LEGO1/omni/include/mxmusicmanager.h
+++ b/LEGO1/omni/include/mxmusicmanager.h
@@ -38,7 +38,7 @@ class MxMusicManager : public MxAudioManager {
 	void SetMIDIVolume();
 
 	static void CALLBACK
-	MidiCallbackProc(HMIDIOUT p_hmo, UINT p_wMsg, DWORD_PTR p_dwInstance, DWORD_PTR p_dwParam1, DWORD_PTR p_dwParam2);
+	MxMusicManager::MidiCallbackProc(HDRVR p_hdrvr, UINT p_uMsg, DWORD p_dwUser, DWORD p_dw1, DWORD p_dw2);
 
 	HMIDISTRM m_midiStreamH;     // 0x30
 	MxBool m_midiInitialized;    // 0x34
diff --git a/LEGO1/omni/src/audio/mxmusicmanager.cpp b/LEGO1/omni/src/audio/mxmusicmanager.cpp
index 3f2a4dd5..09fbc861 100644
--- a/LEGO1/omni/src/audio/mxmusicmanager.cpp
+++ b/LEGO1/omni/src/audio/mxmusicmanager.cpp
@@ -129,16 +129,10 @@ void MxMusicManager::SetMIDIVolume()
 }
 
 // FUNCTION: LEGO1 0x100c0820
-void CALLBACK MxMusicManager::MidiCallbackProc(
-	HMIDIOUT p_hmo,
-	UINT p_wMsg,
-	DWORD_PTR p_dwInstance,
-	DWORD_PTR p_dwParam1,
-	DWORD_PTR p_dwParam2
-)
+void CALLBACK MxMusicManager::MidiCallbackProc(HDRVR p_hdrvr, UINT p_uMsg, DWORD p_dwUser, DWORD p_dw1, DWORD p_dw2)
 {
-	if (p_wMsg == MOM_DONE)
-		((MxMusicManager*) p_dwInstance)->ResetStream();
+	if (p_uMsg == MOM_DONE)
+		((MxMusicManager*) p_dwUser)->ResetStream();
 }
 
 // FUNCTION: LEGO1 0x100c0840
diff --git a/util/compat.h b/util/compat.h
index a5b7a487..b38a1c7c 100644
--- a/util/compat.h
+++ b/util/compat.h
@@ -15,11 +15,6 @@
 #define COMPAT_CONST
 #endif
 
-// DWORD_PTR didn't exist in older Windows SDKs
-#if (defined(_MSC_VER) && _MSC_VER < 1100)
-typedef unsigned long DWORD_PTR, *PDWORD_PTR;
-#endif
-
 // Disable "identifier was truncated to '255' characters" warning.
 // Impossible to avoid this if using STL map or set.
 // This removes most (but not all) occurrences of the warning.