diff --git a/reactos/win32ss/gdi/eng/engwindow.c b/reactos/win32ss/gdi/eng/engwindow.c
index 71910bb2e74..3338076ea2e 100644
--- a/reactos/win32ss/gdi/eng/engwindow.c
+++ b/reactos/win32ss/gdi/eng/engwindow.c
@@ -104,7 +104,7 @@ IntEngWindowChanged(
 
     ASSERT_IRQL_LESS_OR_EQUAL(PASSIVE_LEVEL);
 
-    Clip = UserGetProp(Window, AtomWndObj);
+    Clip = UserGetProp(Window, AtomWndObj, TRUE);
     if (!Clip)
     {
         return;
@@ -208,7 +208,7 @@ EngCreateWnd(
     Clip->PixelFormat = iPixelFormat;
 
     /* associate object with window */
-    UserSetProp(Window, AtomWndObj, Clip);
+    UserSetProp(Window, AtomWndObj, Clip, TRUE);
     ++gcountPWO;
 
     TRACE("EngCreateWnd: SUCCESS: %p!\n", WndObjUser);
@@ -253,7 +253,7 @@ EngDeleteWnd(
     else
     {
         /* Remove object from window */
-        UserRemoveProp(Window, AtomWndObj);
+        UserRemoveProp(Window, AtomWndObj, TRUE);
     }
     --gcountPWO;
 
diff --git a/reactos/win32ss/include/ntuser.h b/reactos/win32ss/include/ntuser.h
index 22cdea82840..6e396eb6aaf 100644
--- a/reactos/win32ss/include/ntuser.h
+++ b/reactos/win32ss/include/ntuser.h
@@ -1029,6 +1029,8 @@ typedef struct _PROPLISTITEM
     HANDLE Data;
 } PROPLISTITEM, *PPROPLISTITEM;
 
+#define PROPERTY_FLAG_SYSTEM 1
+
 typedef struct _PROPERTY
 {
     LIST_ENTRY PropListEntry;
diff --git a/reactos/win32ss/user/ntuser/dde.c b/reactos/win32ss/user/ntuser/dde.c
index 3850bd9d2ee..3c3a11c1965 100644
--- a/reactos/win32ss/user/ntuser/dde.c
+++ b/reactos/win32ss/user/ntuser/dde.c
@@ -339,7 +339,7 @@ IntDdeGetMessageHook(PMSG pMsg, LONG_PTR ExtraInfo)
 
    if (pMsg->message == WM_DDE_TERMINATE)
    {
-      pddeProp = (PDDE_PROP)UserGetProp(pWnd, AtomDDETrack);
+      pddeProp = (PDDE_PROP)UserGetProp(pWnd, AtomDDETrack, TRUE);
       if (pddeProp)
       {
          pWndClient = UserGetWindowObject((HWND)pMsg->wParam);
@@ -348,7 +348,7 @@ IntDdeGetMessageHook(PMSG pMsg, LONG_PTR ExtraInfo)
             ERR("DDE Get Client WM_DDE_TERMINATE\n");
          }
 
-         UserRemoveProp(pWnd, AtomDDETrack);
+         UserRemoveProp(pWnd, AtomDDETrack, TRUE);
          ExFreePoolWithTag(pddeProp, USERTAG_DDE1);
       }
       return TRUE;
@@ -419,7 +419,7 @@ IntDdeSendMessageHook(PWND pWnd, UINT Msg, WPARAM wParam, LPARAM lParam)
       pddeProp->spwnd        = pWndServer;
       pddeProp->spwndPartner = pWnd;
 
-      UserSetProp(pWndServer, AtomDDETrack, (HANDLE)pddeProp);
+      UserSetProp(pWndServer, AtomDDETrack, (HANDLE)pddeProp, TRUE);
    }
    return TRUE;
 }
diff --git a/reactos/win32ss/user/ntuser/defwnd.c b/reactos/win32ss/user/ntuser/defwnd.c
index 044d6f6c92e..36cc914cb57 100644
--- a/reactos/win32ss/user/ntuser/defwnd.c
+++ b/reactos/win32ss/user/ntuser/defwnd.c
@@ -441,8 +441,8 @@ DefWndSetIcon(PWND pWnd, WPARAM wParam, LPARAM lParam)
         EngSetLastError(ERROR_INVALID_PARAMETER);
         return 0;
     }
-    hIconSmall = UserGetProp(pWnd, gpsi->atomIconSmProp);
-    hIcon      = UserGetProp(pWnd, gpsi->atomIconProp);
+    hIconSmall = UserGetProp(pWnd, gpsi->atomIconSmProp, TRUE);
+    hIcon      = UserGetProp(pWnd, gpsi->atomIconProp, TRUE);
 
     hIconOld = wParam == ICON_BIG ? hIcon : hIconSmall;
 
@@ -460,8 +460,8 @@ DefWndSetIcon(PWND pWnd, WPARAM wParam, LPARAM lParam)
             break;
     }
 
-    UserSetProp(pWnd, gpsi->atomIconProp, hIcon);
-    UserSetProp(pWnd, gpsi->atomIconSmProp, hIconSmall);
+    UserSetProp(pWnd, gpsi->atomIconProp, hIcon, TRUE);
+    UserSetProp(pWnd, gpsi->atomIconSmProp, hIconSmall, TRUE);
 
     if ((pWnd->style & WS_CAPTION ) == WS_CAPTION)
        UserPaintCaption(pWnd, DC_ICON);
@@ -481,11 +481,11 @@ DefWndGetIcon(PWND pWnd, WPARAM wParam, LPARAM lParam)
     switch(wParam)
     {
         case ICON_BIG:
-            hIconRet = UserGetProp(pWnd, gpsi->atomIconProp);
+            hIconRet = UserGetProp(pWnd, gpsi->atomIconProp, TRUE);
             break;
         case ICON_SMALL:
         case ICON_SMALL2:
-            hIconRet = UserGetProp(pWnd, gpsi->atomIconSmProp);
+            hIconRet = UserGetProp(pWnd, gpsi->atomIconSmProp, TRUE);
             break;
         default:
             break;
diff --git a/reactos/win32ss/user/ntuser/layered.c b/reactos/win32ss/user/ntuser/layered.c
index ff927e84566..67357549535 100644
--- a/reactos/win32ss/user/ntuser/layered.c
+++ b/reactos/win32ss/user/ntuser/layered.c
@@ -22,7 +22,7 @@ typedef struct _LRD_PROP
 BOOL FASTCALL
 GetLayeredStatus(PWND pWnd)
 {
-   PLRD_PROP pLrdProp = UserGetProp(pWnd, AtomLayer);
+   PLRD_PROP pLrdProp = UserGetProp(pWnd, AtomLayer, TRUE);
    if (pLrdProp)
    {
       return pLrdProp->is_Layered;
@@ -33,7 +33,7 @@ GetLayeredStatus(PWND pWnd)
 BOOL FASTCALL
 SetLayeredStatus(PWND pWnd, BYTE set)
 {
-   PLRD_PROP pLrdProp = UserGetProp(pWnd, AtomLayer);
+   PLRD_PROP pLrdProp = UserGetProp(pWnd, AtomLayer, TRUE);
    if (pLrdProp)
    {
       pLrdProp->is_Layered = set;
@@ -57,7 +57,7 @@ IntSetLayeredWindowAttributes(PWND pWnd,
       return FALSE;
    }
 
-   pLrdProp = UserGetProp(pWnd, AtomLayer);
+   pLrdProp = UserGetProp(pWnd, AtomLayer, TRUE);
 
    if (!pLrdProp)
    {
@@ -68,7 +68,7 @@ IntSetLayeredWindowAttributes(PWND pWnd,
          return FALSE;
       }
       RtlZeroMemory(pLrdProp, sizeof(LRD_PROP));
-      UserSetProp(pWnd, AtomLayer, (HANDLE)pLrdProp);
+      UserSetProp(pWnd, AtomLayer, (HANDLE)pLrdProp, TRUE);
    }
 
    if (pLrdProp)
@@ -258,7 +258,7 @@ NtUserGetLayeredWindowAttributes(
       goto Exit;
    }
 
-   pLrdProp = UserGetProp(pWnd, AtomLayer);
+   pLrdProp = UserGetProp(pWnd, AtomLayer, TRUE);
 
    if (!pLrdProp)
    {
diff --git a/reactos/win32ss/user/ntuser/nonclient.c b/reactos/win32ss/user/ntuser/nonclient.c
index 1cf3265e2c5..00c4398a9e3 100644
--- a/reactos/win32ss/user/ntuser/nonclient.c
+++ b/reactos/win32ss/user/ntuser/nonclient.c
@@ -606,8 +606,8 @@ PCURICON_OBJECT FASTCALL NC_IconForWindow( PWND pWnd )
    //FIXME: This is bad and we should feel bad.
    //FIXME: Stop whining over wine code.
 
-   hIcon = UserGetProp(pWnd, gpsi->atomIconSmProp);
-   if (!hIcon) hIcon = UserGetProp(pWnd, gpsi->atomIconProp);
+   hIcon = UserGetProp(pWnd, gpsi->atomIconSmProp, TRUE);
+   if (!hIcon) hIcon = UserGetProp(pWnd, gpsi->atomIconProp, TRUE);
 
    if (!hIcon && pWnd->pcls->spicnSm)
        return pWnd->pcls->spicnSm;
diff --git a/reactos/win32ss/user/ntuser/painting.c b/reactos/win32ss/user/ntuser/painting.c
index f5d82fda247..94abd8a8dd4 100644
--- a/reactos/win32ss/user/ntuser/painting.c
+++ b/reactos/win32ss/user/ntuser/painting.c
@@ -1189,7 +1189,7 @@ IntFlashWindowEx(PWND pWnd, PFLASHWINFO pfwi)
 
    ASSERT(pfwi);
 
-   FlashState = (DWORD)UserGetProp(pWnd, AtomFlashWndState);
+   FlashState = (DWORD)UserGetProp(pWnd, AtomFlashWndState, TRUE);
 
    if (FlashState == FLASHW_FINISHED)
    {
@@ -1267,7 +1267,7 @@ IntFlashWindowEx(PWND pWnd, PFLASHWINFO pfwi)
          IntKillTimer(pWnd, ID_EVENT_SYSTIMER_FLASHWIN, TRUE);
       }
 
-      UserRemoveProp(pWnd, AtomFlashWndState);
+      UserRemoveProp(pWnd, AtomFlashWndState, TRUE);
    }
    else
    {  // Have a count and started, set timer.
@@ -1305,7 +1305,7 @@ IntFlashWindowEx(PWND pWnd, PFLASHWINFO pfwi)
          FlashState ^= (FlashState ^ pfwi->dwFlags) & (FLASHW_MASK & ~FLASHW_TIMER);
       }
       FlashState = MAKELONG(LOWORD(FlashState),uCount);
-      UserSetProp(pWnd, AtomFlashWndState, (HANDLE) FlashState);
+      UserSetProp(pWnd, AtomFlashWndState, (HANDLE)FlashState, TRUE);
    }
    return Ret;
 }
diff --git a/reactos/win32ss/user/ntuser/prop.c b/reactos/win32ss/user/ntuser/prop.c
index 4429dbe9789..e325ed45cfa 100644
--- a/reactos/win32ss/user/ntuser/prop.c
+++ b/reactos/win32ss/user/ntuser/prop.c
@@ -15,11 +15,13 @@ PPROPERTY
 FASTCALL
 IntGetProp(
     _In_ PWND Window,
-    _In_ ATOM Atom)
+    _In_ ATOM Atom,
+    _In_ BOOLEAN SystemProp)
 {
     PLIST_ENTRY ListEntry;
     PPROPERTY Property;
     UINT i;
+    WORD SystemFlag = SystemProp ? PROPERTY_FLAG_SYSTEM : 0;
 
     NT_ASSERT(UserIsEntered());
     ListEntry = Window->PropListHead.Flink;
@@ -27,33 +29,29 @@ IntGetProp(
     for (i = 0; i < Window->PropListItems; i++)
     {
         Property = CONTAINING_RECORD(ListEntry, PROPERTY, PropListEntry);
-
-        if (ListEntry == NULL)
-        {
-            ERR("Corrupted (or uninitialized?) property list for window %p. Prop count %u. Atom %u.\n",
-                Window, Window->PropListItems, Atom);
-            return NULL;
-        }
-
-        if (Property->Atom == Atom)
-        {
-            return(Property);
-        }
         ListEntry = ListEntry->Flink;
+
+        if (Property->Atom == Atom &&
+            (Property->fs & PROPERTY_FLAG_SYSTEM) == SystemFlag)
+        {
+            return Property;
+        }
     }
-    return(NULL);
+    NT_ASSERT(ListEntry == &Window->PropListHead);
+    return NULL;
 }
 
 HANDLE
 FASTCALL
 UserGetProp(
     _In_ PWND Window,
-    _In_ ATOM Atom)
+    _In_ ATOM Atom,
+    _In_ BOOLEAN SystemProp)
 {
     PPROPERTY Prop;
 
     NT_ASSERT(UserIsEntered());
-    Prop = IntGetProp(Window, Atom);
+    Prop = IntGetProp(Window, Atom, SystemProp);
     return Prop ? Prop->Data : NULL;
 }
 
@@ -62,13 +60,14 @@ HANDLE
 FASTCALL
 UserRemoveProp(
     _In_ PWND Window,
-    _In_ ATOM Atom)
+    _In_ ATOM Atom,
+    _In_ BOOLEAN SystemProp)
 {
     PPROPERTY Prop;
     HANDLE Data;
 
     NT_ASSERT(UserIsEnteredExclusive());
-    Prop = IntGetProp(Window, Atom);
+    Prop = IntGetProp(Window, Atom, SystemProp);
     if (Prop == NULL)
     {
         return NULL;
@@ -87,12 +86,13 @@ FASTCALL
 UserSetProp(
     _In_ PWND Window,
     _In_ ATOM Atom,
-    _In_ HANDLE Data)
+    _In_ HANDLE Data,
+    _In_ BOOLEAN SystemProp)
 {
     PPROPERTY Prop;
 
     NT_ASSERT(UserIsEnteredExclusive());
-    Prop = IntGetProp(Window, Atom);
+    Prop = IntGetProp(Window, Atom, SystemProp);
     if (Prop == NULL)
     {
         Prop = UserHeapAlloc(sizeof(PROPERTY));
@@ -101,6 +101,7 @@ UserSetProp(
             return FALSE;
         }
         Prop->Atom = Atom;
+        Prop->fs = SystemProp ? PROPERTY_FLAG_SYSTEM : 0;
         InsertTailList(&Window->PropListHead, &Prop->PropListEntry);
         Window->PropListItems++;
     }
@@ -171,24 +172,28 @@ NtUserBuildPropList(
                (ListEntry != &Window->PropListHead))
         {
             Property = CONTAINING_RECORD(ListEntry, PROPERTY, PropListEntry);
-            listitem.Atom = Property->Atom;
-            listitem.Data = Property->Data;
-
-            Status = MmCopyToCaller(li, &listitem, sizeof(PROPLISTITEM));
-            if (!NT_SUCCESS(Status))
-            {
-                goto Exit;
-            }
-
-            BufferSize -= sizeof(PROPLISTITEM);
-            Cnt++;
-            li++;
             ListEntry = ListEntry->Flink;
+            if (!(Property->fs & PROPERTY_FLAG_SYSTEM))
+            {
+                listitem.Atom = Property->Atom;
+                listitem.Data = Property->Data;
+
+                Status = MmCopyToCaller(li, &listitem, sizeof(PROPLISTITEM));
+                if (!NT_SUCCESS(Status))
+                {
+                    goto Exit;
+                }
+
+                BufferSize -= sizeof(PROPLISTITEM);
+                Cnt++;
+                li++;
+            }
         }
 
     }
     else
     {
+        /* FIXME: This counts user and system props */
         Cnt = Window->PropListItems * sizeof(PROPLISTITEM);
     }
 
@@ -228,7 +233,7 @@ NtUserRemoveProp(
         goto Exit;
     }
 
-    Data = UserRemoveProp(Window, Atom);
+    Data = UserRemoveProp(Window, Atom, FALSE);
 
 Exit:
     TRACE("Leave NtUserRemoveProp, ret=%p\n", Data);
@@ -257,7 +262,7 @@ NtUserSetProp(
         goto Exit;
     }
 
-    Ret = UserSetProp(Window, Atom, Data);
+    Ret = UserSetProp(Window, Atom, Data, FALSE);
 
 Exit:
     TRACE("Leave NtUserSetProp, ret=%i\n", Ret);
diff --git a/reactos/win32ss/user/ntuser/prop.h b/reactos/win32ss/user/ntuser/prop.h
index 8d832748b05..7c5beb8703b 100644
--- a/reactos/win32ss/user/ntuser/prop.h
+++ b/reactos/win32ss/user/ntuser/prop.h
@@ -4,13 +4,15 @@ HANDLE
 FASTCALL
 UserGetProp(
     _In_ PWND Window,
-    _In_ ATOM Atom);
+    _In_ ATOM Atom,
+    _In_ BOOLEAN SystemProp);
 
 HANDLE
 FASTCALL
 UserRemoveProp(
     _In_ PWND Window,
-    _In_ ATOM Atom);
+    _In_ ATOM Atom,
+    _In_ BOOLEAN SystemProp);
 
 _Success_(return)
 BOOL
@@ -18,7 +20,8 @@ FASTCALL
 UserSetProp(
     _In_ PWND Window,
     _In_ ATOM Atom,
-    _In_ HANDLE Data);
+    _In_ HANDLE Data,
+    _In_ BOOLEAN SystemProp);
 
 VOID
 FASTCALL
diff --git a/reactos/win32ss/user/ntuser/simplecall.c b/reactos/win32ss/user/ntuser/simplecall.c
index 7fef2c7961b..86d9cee7415 100644
--- a/reactos/win32ss/user/ntuser/simplecall.c
+++ b/reactos/win32ss/user/ntuser/simplecall.c
@@ -610,7 +610,7 @@ NtUserCallHwnd(
             return 0;
          }
 
-         HelpId = (DWORD)(DWORD_PTR)UserGetProp(Window, gpsi->atomContextHelpIdProp);
+         HelpId = (DWORD)(DWORD_PTR)UserGetProp(Window, gpsi->atomContextHelpIdProp, TRUE);
 
          UserLeave();
          return HelpId;
@@ -666,9 +666,9 @@ NtUserCallHwndParam(
          }
 
          if ( Param )
-            UserSetProp(Window, gpsi->atomContextHelpIdProp, (HANDLE)Param);
+            UserSetProp(Window, gpsi->atomContextHelpIdProp, (HANDLE)Param, TRUE);
          else
-            UserRemoveProp(Window, gpsi->atomContextHelpIdProp);
+            UserRemoveProp(Window, gpsi->atomContextHelpIdProp, TRUE);
 
          UserLeave();
          return TRUE;
diff --git a/reactos/win32ss/user/ntuser/windc.c b/reactos/win32ss/user/ntuser/windc.c
index 521a312b472..7427b9fe11c 100644
--- a/reactos/win32ss/user/ntuser/windc.c
+++ b/reactos/win32ss/user/ntuser/windc.c
@@ -967,7 +967,7 @@ UserGethWnd( HDC hdc, PWNDOBJ *pwndo)
 
   if (hWnd && (Wnd = UserGetWindowObject(hWnd)))
   {
-     Clip = (XCLIPOBJ*)UserGetProp(Wnd, AtomWndObj);
+     Clip = (XCLIPOBJ*)UserGetProp(Wnd, AtomWndObj, TRUE);
 
      if ( Clip && Clip->Hwnd == hWnd )
      {
diff --git a/reactos/win32ss/user/ntuser/window.c b/reactos/win32ss/user/ntuser/window.c
index 46baca6d7fd..bcc915e4eb7 100644
--- a/reactos/win32ss/user/ntuser/window.c
+++ b/reactos/win32ss/user/ntuser/window.c
@@ -373,7 +373,7 @@ DWORD FASTCALL IntGetWindowContextHelpId( PWND pWnd )
 
    do
    {
-      HelpId = (DWORD)(DWORD_PTR)UserGetProp(pWnd, gpsi->atomContextHelpIdProp);
+      HelpId = (DWORD)(DWORD_PTR)UserGetProp(pWnd, gpsi->atomContextHelpIdProp, TRUE);
       if (!HelpId) break;
       pWnd = IntGetParent(pWnd);
    }
diff --git a/reactos/win32ss/user/user32/include/user32p.h b/reactos/win32ss/user/user32/include/user32p.h
index 8e29ab41d05..466c0cbd77b 100644
--- a/reactos/win32ss/user/user32/include/user32p.h
+++ b/reactos/win32ss/user/user32/include/user32p.h
@@ -133,7 +133,7 @@ BOOL UserDrawSysMenuButton( HWND hWnd, HDC hDC, LPRECT, BOOL down );
 HWND* WIN_ListChildren (HWND hWndparent);
 VOID DeleteFrameBrushes(VOID);
 BOOL WINAPI GdiValidateHandle(HGDIOBJ);
-HANDLE FASTCALL UserGetProp(HWND hWnd, ATOM Atom);
+HANDLE FASTCALL UserGetProp(HWND hWnd, ATOM Atom, BOOLEAN SystemProp);
 BOOL WINAPI InitializeImmEntryTable(VOID);
 
 /* EOF */
diff --git a/reactos/win32ss/user/user32/windows/defwnd.c b/reactos/win32ss/user/user32/windows/defwnd.c
index 9b6e1bd4da4..b255338230b 100644
--- a/reactos/win32ss/user/user32/windows/defwnd.c
+++ b/reactos/win32ss/user/user32/windows/defwnd.c
@@ -397,11 +397,11 @@ DefWndGetIcon(PWND pWnd, WPARAM wParam, LPARAM lParam)
     switch(wParam)
     {
         case ICON_BIG:
-            hIconRet = UserGetProp(UserHMGetHandle(pWnd), gpsi->atomIconProp);
+            hIconRet = UserGetProp(UserHMGetHandle(pWnd), gpsi->atomIconProp, TRUE);
             break;
         case ICON_SMALL:
         case ICON_SMALL2:
-            hIconRet = UserGetProp(UserHMGetHandle(pWnd), gpsi->atomIconSmProp);
+            hIconRet = UserGetProp(UserHMGetHandle(pWnd), gpsi->atomIconSmProp, TRUE);
             break;
         default:
             break;
diff --git a/reactos/win32ss/user/user32/windows/prop.c b/reactos/win32ss/user/user32/windows/prop.c
index d57f4dc9e9f..ce4d130cbb5 100644
--- a/reactos/win32ss/user/user32/windows/prop.c
+++ b/reactos/win32ss/user/user32/windows/prop.c
@@ -35,12 +35,13 @@
 
 HANDLE
 FASTCALL
-IntGetProp(HWND hWnd, ATOM Atom)
+IntGetProp(HWND hWnd, ATOM Atom, BOOLEAN SystemProp)
 {
   PLIST_ENTRY ListEntry, temp;
   PPROPERTY Property;
   PWND pWnd;
   int i;
+  WORD SystemFlag = SystemProp ? PROPERTY_FLAG_SYSTEM : 0;
 
   pWnd = ValidateHwnd(hWnd);
   if (!pWnd) return NULL;
@@ -49,7 +50,8 @@ IntGetProp(HWND hWnd, ATOM Atom)
   for (i = 0; i < pWnd->PropListItems; i++ )
   {
       Property = CONTAINING_RECORD(ListEntry, PROPERTY, PropListEntry);
-      if (Property->Atom == Atom)
+      if (Property->Atom == Atom &&
+          (Property->fs & PROPERTY_FLAG_SYSTEM) == SystemFlag)
       {
          return(Property);
       }
@@ -61,10 +63,10 @@ IntGetProp(HWND hWnd, ATOM Atom)
 
 HANDLE
 FASTCALL
-UserGetProp(HWND hWnd, ATOM Atom)
+UserGetProp(HWND hWnd, ATOM Atom, BOOLEAN SystemProp)
 {
   PPROPERTY Prop;
-  Prop = IntGetProp(hWnd, Atom);
+  Prop = IntGetProp(hWnd, Atom, SystemProp);
   return Prop ? Prop->Data : NULL;
 }
 
@@ -383,7 +385,7 @@ GetPropW(HWND hWnd, LPCWSTR lpString)
   {
      Atom = LOWORD((DWORD_PTR)lpString);
   }
-  Prop = IntGetProp(hWnd, Atom);
+  Prop = IntGetProp(hWnd, Atom, FALSE);
   if (Prop != NULL) Data = Prop->Data;
   return Data;
 }