diff --git a/reactos/dll/win32/mmdrv/common.c b/reactos/dll/win32/mmdrv/common.c
index 8d64b2ff496..bb32b8052a9 100644
--- a/reactos/dll/win32/mmdrv/common.c
+++ b/reactos/dll/win32/mmdrv/common.c
@@ -80,8 +80,8 @@ GetDeviceCount(DeviceType device_type)
 DWORD
 GetDeviceCapabilities(
     DeviceType device_type,
-    DWORD device_id,
-    PVOID capabilities,
+    UINT device_id,
+    DWORD_PTR capabilities,
     DWORD capabilities_size)
 {
     MMRESULT result;
@@ -149,10 +149,10 @@ GetDeviceCapabilities(
 DWORD
 OpenDevice(
     DeviceType device_type,
-    DWORD device_id,
+    UINT device_id,
     PVOID open_descriptor,
     DWORD flags,
-    DWORD private_handle)
+    DWORD_PTR private_handle)
 {
     SessionInfo* session_info;
     MMRESULT result;
@@ -234,7 +234,7 @@ OpenDevice(
 
 DWORD
 CloseDevice(
-    DWORD private_handle)
+    DWORD_PTR private_handle)
 {
     MMRESULT result;
     SessionInfo* session_info = (SessionInfo*) private_handle;
diff --git a/reactos/dll/win32/mmdrv/kernel.c b/reactos/dll/win32/mmdrv/kernel.c
index efba1fce75a..07ae0be2556 100644
--- a/reactos/dll/win32/mmdrv/kernel.c
+++ b/reactos/dll/win32/mmdrv/kernel.c
@@ -22,7 +22,7 @@
 MMRESULT
 CobbleDeviceName(
     DeviceType device_type,
-    DWORD device_id,
+    UINT device_id,
     PWCHAR out_device_name)
 {
     WCHAR base_device_name[MAX_DEVICE_NAME_LENGTH];
@@ -78,7 +78,7 @@ CobbleDeviceName(
 MMRESULT
 OpenKernelDevice(
     DeviceType device_type,
-    DWORD device_id,
+    UINT device_id,
     DWORD access,
     HANDLE* handle)
 {
diff --git a/reactos/dll/win32/mmdrv/mmdrv.h b/reactos/dll/win32/mmdrv/mmdrv.h
index 7b17bcb00c3..241dca9f038 100644
--- a/reactos/dll/win32/mmdrv/mmdrv.h
+++ b/reactos/dll/win32/mmdrv/mmdrv.h
@@ -127,7 +127,7 @@ typedef struct _SessionInfo
     struct _SessionInfo* next;
 
     DeviceType device_type;
-    DWORD device_id;
+    UINT device_id;
 
     HANDLE kernel_device_handle;
 
@@ -143,8 +143,8 @@ typedef struct _SessionInfo
     BOOL is_paused;
 
     /* Stuff passed to us from winmm */
-    DWORD app_user_data;
-    DWORD callback;
+    DWORD_PTR app_user_data;
+    DWORD_PTR callback;
 
     DWORD flags;
 
@@ -181,8 +181,8 @@ BOOL
 NotifyClient(
     SessionInfo* session_info,
     DWORD message,
-    DWORD parameter1,
-    DWORD parameter2);
+    DWORD_PTR parameter1,
+    DWORD_PTR parameter2);
 
 
 /*
@@ -198,13 +198,13 @@ ErrorToMmResult(UINT error_code);
 MMRESULT
 CobbleDeviceName(
     DeviceType device_type,
-    DWORD device_id,
+    UINT device_id,
     PWCHAR out_device_name);
 
 MMRESULT
 OpenKernelDevice(
     DeviceType device_type,
-    DWORD device_id,
+    UINT device_id,
     DWORD access,
     HANDLE* handle);
 
@@ -231,7 +231,7 @@ GetDeviceData(
 MMRESULT
 CreateSession(
     DeviceType device_type,
-    DWORD device_id,
+    UINT device_id,
     SessionInfo** session_info);
 
 VOID
@@ -240,7 +240,7 @@ DestroySession(SessionInfo* session);
 SessionInfo*
 GetSession(
     DeviceType device_type,
-    DWORD device_id);
+    UINT device_id);
 
 MMRESULT
 StartSessionThread(SessionInfo* session_info);
@@ -253,9 +253,9 @@ CallSessionThread(
 
 DWORD
 HandleBySessionThread(
-    DWORD private_handle,
-    DWORD message,
-    DWORD parameter);
+    DWORD_PTR private_handle,
+    DWORD_PTR message,
+    DWORD_PTR parameter);
 
 
 /* General */
@@ -266,21 +266,21 @@ GetDeviceCount(DeviceType device_type);
 DWORD
 GetDeviceCapabilities(
     DeviceType device_type,
-    DWORD device_id,
-    PVOID capabilities,
+    UINT device_id,
+    DWORD_PTR capabilities,
     DWORD capabilities_size);
 
 DWORD
 OpenDevice(
     DeviceType device_type,
-    DWORD device_id,
+    UINT device_id,
     PVOID open_descriptor,
     DWORD flags,
-    DWORD private_handle);
+    DWORD_PTR private_handle);
 
 DWORD
 CloseDevice(
-    DWORD private_handle);
+    DWORD_PTR private_handle);
 
 DWORD
 PauseDevice(
@@ -310,7 +310,7 @@ QueryWaveFormat(
 
 DWORD
 WriteWaveBuffer(
-    DWORD private_handle,
+    DWORD_PTR private_handle,
     PWAVEHDR wave_header,
     DWORD wave_header_size);
 
diff --git a/reactos/dll/win32/mmdrv/mme.c b/reactos/dll/win32/mmdrv/mme.c
index 82ca3e2755c..26cb285fb2a 100644
--- a/reactos/dll/win32/mmdrv/mme.c
+++ b/reactos/dll/win32/mmdrv/mme.c
@@ -22,8 +22,8 @@ BOOL
 NotifyClient(
     SessionInfo* session_info,
     DWORD message,
-    DWORD parameter1,
-    DWORD parameter2)
+    DWORD_PTR parameter1,
+    DWORD_PTR parameter2)
 {
     return DriverCallback(session_info->callback,
                           HIWORD(session_info->flags),
@@ -43,11 +43,11 @@ NotifyClient(
 
 APIENTRY DWORD
 wodMessage(
-    DWORD device_id,
-    DWORD message,
-    DWORD private_handle,
-    DWORD parameter1,
-    DWORD parameter2)
+    UINT device_id,
+    UINT message,
+    DWORD_PTR private_handle,
+    DWORD_PTR parameter1,
+    DWORD_PTR parameter2)
 {
     switch ( message )
     {
@@ -61,7 +61,7 @@ wodMessage(
             DPRINT("WODM_GETDEVCAPS\n");
             return GetDeviceCapabilities(WaveOutDevice,
                                          device_id,
-                                         (PVOID) parameter1,
+                                         parameter1,
                                          parameter2);
 
         /* http://www.osronline.com/ddkx/w98ddk/mmedia_4p85.htm */
diff --git a/reactos/dll/win32/mmdrv/session.c b/reactos/dll/win32/mmdrv/session.c
index b9d63e7d9b5..cc79771ce81 100644
--- a/reactos/dll/win32/mmdrv/session.c
+++ b/reactos/dll/win32/mmdrv/session.c
@@ -26,7 +26,7 @@ CRITICAL_SECTION session_lock;
 SessionInfo*
 GetSession(
     DeviceType device_type,
-    DWORD device_id)
+    UINT device_id)
 {
     SessionInfo* session_info;
 
@@ -59,7 +59,7 @@ GetSession(
 MMRESULT
 CreateSession(
     DeviceType device_type,
-    DWORD device_id,
+    UINT device_id,
     SessionInfo** session_info)
 {
     HANDLE heap = GetProcessHeap();
@@ -186,7 +186,7 @@ StartSessionThread(SessionInfo* session_info)
 
     result = mmTaskCreate(task,
                           &session_info->thread.handle,
-                          (DWORD) session_info);
+                          (DWORD_PTR)session_info);
 
     if ( result != MMSYSERR_NOERROR )
     {
@@ -235,9 +235,9 @@ CallSessionThread(
 
 DWORD
 HandleBySessionThread(
-    DWORD private_handle,
-    DWORD message,
-    DWORD parameter)
+    DWORD_PTR private_handle,
+    DWORD_PTR message,
+    DWORD_PTR parameter)
 {
     return CallSessionThread((SessionInfo*) private_handle,
                              message,
diff --git a/reactos/dll/win32/mmdrv/wave.c b/reactos/dll/win32/mmdrv/wave.c
index c3169220000..fb688de20a5 100644
--- a/reactos/dll/win32/mmdrv/wave.c
+++ b/reactos/dll/win32/mmdrv/wave.c
@@ -56,7 +56,7 @@ QueueWaveBuffer(
     wave_header->dwFlags |= WHDR_INQUEUE;
 
     /* Save our handle in the header */
-    wave_header->reserved = (DWORD) session_info;
+    wave_header->reserved = (DWORD_PTR) session_info;
 
     /* Locate the end of the queue */
     previous_node = NULL;
@@ -112,10 +112,10 @@ ReturnCompletedBuffers(SessionInfo* session_info)
             message = (session_info->device_type == WaveOutDevice) ? WOM_DONE :
                                                                      WIM_DATA;
 
-            DPRINT("Notifying client that buffer 0x%x is done\n", (int) header);
+            DPRINT("Notifying client that buffer 0x%x is done\n", header);
 
             /* Notify the client */
-            NotifyClient(session_info, message, (DWORD) header, 0);
+            NotifyClient(session_info, message, (DWORD_PTR) header, 0);
         }
     }
 
@@ -369,7 +369,7 @@ SetWaveFormat(
 
 DWORD
 WriteWaveBuffer(
-    DWORD private_handle,
+    DWORD_PTR private_handle,
     PWAVEHDR wave_header,
     DWORD wave_header_size)
 {