diff --git a/dlls/user.exe16/message.c b/dlls/user.exe16/message.c
index b2b5ce947b1..d244f752b36 100644
--- a/dlls/user.exe16/message.c
+++ b/dlls/user.exe16/message.c
@@ -2583,9 +2583,11 @@ HWND create_window16( CREATESTRUCTW *cs, LPCWSTR className, HINSTANCE instance,
 }
 
 
-static void WINAPI User16CallFreeIcon( ULONG *param, ULONG size )
+static NTSTATUS WINAPI User16CallFreeIcon( void *args, ULONG size )
 {
+    ULONG *param = args;
     GlobalFree16( LOWORD(*param) );
+    return STATUS_SUCCESS;
 }
 
 
diff --git a/dlls/user32/class.c b/dlls/user32/class.c
index 0cfdf552a5d..9c7bd3a5c6b 100644
--- a/dlls/user32/class.c
+++ b/dlls/user32/class.c
@@ -19,6 +19,8 @@
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  */
 
+#include "ntstatus.h"
+#define WIN32_NO_STATUS
 #include "user_private.h"
 #include "controls.h"
 #include "wine/debug.h"
@@ -268,7 +270,7 @@ static void load_uxtheme(void)
 /***********************************************************************
  *           User32InitBuiltinClasses
  */
-BOOL WINAPI User32InitBuiltinClasses( const struct win_hook_params *params, ULONG size )
+NTSTATUS WINAPI User32InitBuiltinClasses( void *args, ULONG size )
 {
     DWORD layout;
 
@@ -276,7 +278,7 @@ BOOL WINAPI User32InitBuiltinClasses( const struct win_hook_params *params, ULON
 
     /* Load uxtheme.dll so that standard scrollbars and dialogs are hooked for theming support */
     load_uxtheme();
-    return TRUE;
+    return STATUS_SUCCESS;
 }
 
 
diff --git a/dlls/user32/hook.c b/dlls/user32/hook.c
index 4f5b8d13973..b7d9da6fd5a 100644
--- a/dlls/user32/hook.c
+++ b/dlls/user32/hook.c
@@ -432,12 +432,14 @@ HWINEVENTHOOK WINAPI SetWinEventHook(DWORD event_min, DWORD event_max,
     return NtUserSetWinEventHook( event_min, event_max, inst, &str, proc, pid, tid, flags );
 }
 
-BOOL WINAPI User32CallWinEventHook( const struct win_event_hook_params *params, ULONG size )
+NTSTATUS WINAPI User32CallWinEventHook( void *args, ULONG size )
 {
+    const struct win_event_hook_params *params = args;
     WINEVENTPROC proc = params->proc;
     HMODULE free_module = 0;
 
-    if (params->module[0] && !(proc = get_hook_proc( proc, params->module, &free_module ))) return FALSE;
+    if (params->module[0] && !(proc = get_hook_proc( proc, params->module, &free_module )))
+        return STATUS_INVALID_PARAMETER;
 
     TRACE_(relay)( "\1Call winevent hook proc %p (hhook=%p,event=%lx,hwnd=%p,object_id=%lx,child_id=%lx,tid=%04lx,time=%lx)\n",
                    proc, params->handle, params->event, params->hwnd, params->object_id,
@@ -451,7 +453,7 @@ BOOL WINAPI User32CallWinEventHook( const struct win_event_hook_params *params,
                    params->child_id, params->tid, params->time );
 
     if (free_module) FreeLibrary( free_module );
-    return TRUE;
+    return STATUS_SUCCESS;
 }
 
 NTSTATUS WINAPI User32CallWindowsHook( void *args, ULONG size )
diff --git a/dlls/user32/user_main.c b/dlls/user32/user_main.c
index c27e6add071..9c9270be197 100644
--- a/dlls/user32/user_main.c
+++ b/dlls/user32/user_main.c
@@ -112,7 +112,7 @@ static NTSTATUS WINAPI User32DrawNonClientButton( const struct draw_non_client_b
 {
     user_api->pNonClientButtonDraw( params->hwnd, params->hdc, params->type, params->rect,
                                     params->down, params->grayed );
-    return 0;
+    return STATUS_SUCCESS;
 }
 
 static NTSTATUS WINAPI User32DrawScrollBar( const struct draw_scroll_bar_params *params, ULONG size )
@@ -122,7 +122,7 @@ static NTSTATUS WINAPI User32DrawScrollBar( const struct draw_scroll_bar_params
                               &params->tracking_info, params->arrows, params->interior,
                               &rect, params->enable_flags, params->arrow_size, params->thumb_pos,
                               params->thumb_size, params->vertical );
-    return 0;
+    return STATUS_SUCCESS;
 }
 
 static NTSTATUS WINAPI User32DrawText( void *args, ULONG size )
@@ -136,15 +136,20 @@ static NTSTATUS WINAPI User32DrawText( void *args, ULONG size )
     return NtCallbackReturn( &result, sizeof(result), STATUS_SUCCESS );
 }
 
-static NTSTATUS WINAPI User32ImmProcessKey( const struct imm_process_key_params *params, ULONG size )
+static NTSTATUS WINAPI User32ImmProcessKey( void *args, ULONG size )
 {
-    return ImmProcessKey( params->hwnd, params->hkl, params->vkey, params->key_data, 0 );
+    const struct imm_process_key_params *params = args;
+    if (ImmProcessKey( params->hwnd, params->hkl, params->vkey, params->key_data, 0 ))
+        return STATUS_SUCCESS;
+    return STATUS_INVALID_PARAMETER;
 }
 
-static NTSTATUS WINAPI User32ImmTranslateMessage( const struct imm_translate_message_params *params,
-                                                  ULONG size )
+static NTSTATUS WINAPI User32ImmTranslateMessage( void *args, ULONG size )
 {
-    return ImmTranslateMessage( params->hwnd, params->msg, params->wparam, params->key_data );
+    const struct imm_translate_message_params *params = args;
+    if (ImmTranslateMessage( params->hwnd, params->msg, params->wparam, params->key_data ))
+        return STATUS_SUCCESS;
+    return STATUS_INVALID_PARAMETER;
 }
 
 static NTSTATUS WINAPI User32LoadImage( void *args, ULONG size )
@@ -168,7 +173,7 @@ static NTSTATUS WINAPI User32FreeCachedClipboardData( const struct free_cached_d
                                                       ULONG size )
 {
     free_cached_data( params->format, params->handle );
-    return 0;
+    return STATUS_SUCCESS;
 }
 
 static NTSTATUS WINAPI User32PostDDEMessage( const struct post_dde_message_params *params, ULONG size )
@@ -181,7 +186,7 @@ static NTSTATUS WINAPI User32RenderSsynthesizedFormat( const struct render_synth
                                                        ULONG size )
 {
     render_synthesized_format( params->format, params->from );
-    return 0;
+    return STATUS_SUCCESS;
 }
 
 static NTSTATUS WINAPI User32LoadDriver( void *args, ULONG size )
diff --git a/dlls/user32/user_private.h b/dlls/user32/user_private.h
index 102fee69af2..a9d6a20ddf1 100644
--- a/dlls/user32/user_private.h
+++ b/dlls/user32/user_private.h
@@ -82,11 +82,11 @@ extern ATOM get_class_info( HINSTANCE instance, const WCHAR *name, WNDCLASSEXW *
 /* kernel callbacks */
 
 NTSTATUS WINAPI User32CallEnumDisplayMonitor( void *args, ULONG size );
-BOOL WINAPI User32CallSendAsyncCallback( const struct send_async_params *params, ULONG size );
-BOOL WINAPI User32CallWinEventHook( const struct win_event_hook_params *params, ULONG size );
-BOOL WINAPI User32CallWindowProc( struct win_proc_params *params, ULONG size );
+NTSTATUS WINAPI User32CallSendAsyncCallback( void *args, ULONG size );
+NTSTATUS WINAPI User32CallWinEventHook( void *args, ULONG size );
+NTSTATUS WINAPI User32CallWindowProc( void *args, ULONG size );
 NTSTATUS WINAPI User32CallWindowsHook( void *args, ULONG size );
-BOOL WINAPI User32InitBuiltinClasses( const struct win_hook_params *params, ULONG size );
+NTSTATUS WINAPI User32InitBuiltinClasses( void *args, ULONG size );
 
 /* message spy definitions */
 
diff --git a/dlls/user32/winproc.c b/dlls/user32/winproc.c
index d2e4b29fc44..4525f604beb 100644
--- a/dlls/user32/winproc.c
+++ b/dlls/user32/winproc.c
@@ -19,6 +19,8 @@
  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  */
 
+#include "ntstatus.h"
+#define WIN32_NO_STATUS
 #include "user_private.h"
 #include "controls.h"
 #include "dbt.h"
@@ -802,8 +804,9 @@ void unpack_message( HWND hwnd, UINT message, WPARAM *wparam, LPARAM *lparam, vo
     *lparam = (LPARAM)buffer;
 }
 
-BOOL WINAPI User32CallWindowProc( struct win_proc_params *params, ULONG size )
+NTSTATUS WINAPI User32CallWindowProc( void *args, ULONG size )
 {
+    struct win_proc_params *params = args;
     size_t packed_size = 0;
     void *buffer = NULL;
     LRESULT result;
@@ -824,15 +827,16 @@ BOOL WINAPI User32CallWindowProc( struct win_proc_params *params, ULONG size )
     {
         LRESULT *result_ptr = (LRESULT *)buffer - 1;
         *result_ptr = result;
-        return NtCallbackReturn( result_ptr, sizeof(*result_ptr) + packed_size, TRUE );
+        return NtCallbackReturn( result_ptr, sizeof(*result_ptr) + packed_size, STATUS_SUCCESS );
     }
-    return NtCallbackReturn( &result, sizeof(result), TRUE );
+    return NtCallbackReturn( &result, sizeof(result), STATUS_SUCCESS );
 }
 
-BOOL WINAPI User32CallSendAsyncCallback( const struct send_async_params *params, ULONG size )
+NTSTATUS WINAPI User32CallSendAsyncCallback( void *args, ULONG size )
 {
+    const struct send_async_params *params = args;
     params->callback( params->hwnd, params->msg, params->data, params->result );
-    return TRUE;
+    return STATUS_SUCCESS;
 }
 
 /**********************************************************************
diff --git a/dlls/win32u/defwnd.c b/dlls/win32u/defwnd.c
index cba5f02c02e..cf3af86d161 100644
--- a/dlls/win32u/defwnd.c
+++ b/dlls/win32u/defwnd.c
@@ -1362,8 +1362,7 @@ static BOOL draw_frame_caption( HDC dc, RECT *r, UINT flags )
     return TRUE;
 }
 
-BOOL draw_menu_button( HWND hwnd, HDC dc, RECT *r, enum NONCLIENT_BUTTON_TYPE type, BOOL down,
-                       BOOL grayed )
+void draw_menu_button( HWND hwnd, HDC dc, RECT *r, enum NONCLIENT_BUTTON_TYPE type, BOOL down, BOOL grayed )
 {
     struct draw_non_client_button_params params;
     void *ret_ptr;
@@ -1375,7 +1374,7 @@ BOOL draw_menu_button( HWND hwnd, HDC dc, RECT *r, enum NONCLIENT_BUTTON_TYPE ty
     params.rect = *r;
     params.down = down;
     params.grayed = grayed;
-    return KeUserModeCallback( NtUserDrawNonClientButton, &params, sizeof(params), &ret_ptr, &ret_len );
+    KeUserModeCallback( NtUserDrawNonClientButton, &params, sizeof(params), &ret_ptr, &ret_len );
 }
 
 BOOL draw_frame_menu( HDC dc, RECT *r, UINT flags )
diff --git a/dlls/win32u/imm.c b/dlls/win32u/imm.c
index 05b8b60090f..d612e7ca6e9 100644
--- a/dlls/win32u/imm.c
+++ b/dlls/win32u/imm.c
@@ -614,7 +614,7 @@ BOOL WINAPI ImmProcessKey( HWND hwnd, HKL hkl, UINT vkey, LPARAM key_data, DWORD
         { .hwnd = hwnd, .hkl = hkl, .vkey = vkey, .key_data = key_data };
     void *ret_ptr;
     ULONG ret_len;
-    return KeUserModeCallback( NtUserImmProcessKey, &params, sizeof(params), &ret_ptr, &ret_len );
+    return !KeUserModeCallback( NtUserImmProcessKey, &params, sizeof(params), &ret_ptr, &ret_len );
 }
 
 BOOL WINAPI ImmTranslateMessage( HWND hwnd, UINT msg, WPARAM wparam, LPARAM key_data )
@@ -623,6 +623,5 @@ BOOL WINAPI ImmTranslateMessage( HWND hwnd, UINT msg, WPARAM wparam, LPARAM key_
         { .hwnd = hwnd, .msg = msg, .wparam = wparam, .key_data = key_data };
     void *ret_ptr;
     ULONG ret_len;
-    return KeUserModeCallback( NtUserImmTranslateMessage, &params, sizeof(params),
-                               &ret_ptr, &ret_len );
+    return !KeUserModeCallback( NtUserImmTranslateMessage, &params, sizeof(params), &ret_ptr, &ret_len );
 }
diff --git a/dlls/win32u/win32u_private.h b/dlls/win32u/win32u_private.h
index b08c0ceb716..d5f010a8249 100644
--- a/dlls/win32u/win32u_private.h
+++ b/dlls/win32u/win32u_private.h
@@ -63,7 +63,7 @@ extern void register_window_surface( struct window_surface *old,
 extern LRESULT default_window_proc( HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam,
                                     BOOL ansi );
 extern LRESULT desktop_window_proc( HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam );
-extern BOOL draw_menu_button( HWND hwnd, HDC dc, RECT *r, enum NONCLIENT_BUTTON_TYPE, BOOL down, BOOL grayed );
+extern void draw_menu_button( HWND hwnd, HDC dc, RECT *r, enum NONCLIENT_BUTTON_TYPE, BOOL down, BOOL grayed );
 extern BOOL draw_frame_menu( HDC dc, RECT *r, UINT flags );
 extern BOOL draw_nc_sys_button( HWND hwnd, HDC hdc, BOOL down );
 extern BOOL draw_rect_edge( HDC hdc, RECT *rc, UINT uType, UINT uFlags, UINT width );