Index: /trunk/src/VBox/Additions/WINNT/Graphics/Display/wddm/VBoxUhgsmiKmt.cpp
===================================================================
--- /trunk/src/VBox/Additions/WINNT/Graphics/Display/wddm/VBoxUhgsmiKmt.cpp	(revision 33930)
+++ /trunk/src/VBox/Additions/WINNT/Graphics/Display/wddm/VBoxUhgsmiKmt.cpp	(revision 33931)
@@ -637,5 +637,5 @@
         }
 
-        ReleaseDC(NULL, OpenAdapterData.hDc);
+        DeleteDC(OpenAdapterData.hDc);
     }
 
@@ -651,5 +651,5 @@
     if (!Status)
     {
-        ReleaseDC(NULL, pAdapter->hDc);
+        DeleteDC(pAdapter->hDc);
         return S_OK;
     }
Index: /trunk/src/VBox/Additions/WINNT/VBoxTray/VBoxDispIf.cpp
===================================================================
--- /trunk/src/VBox/Additions/WINNT/VBoxTray/VBoxDispIf.cpp	(revision 33930)
+++ /trunk/src/VBox/Additions/WINNT/VBoxTray/VBoxDispIf.cpp	(revision 33931)
@@ -107,34 +107,77 @@
 }
 
-typedef DECLCALLBACK(BOOLEAN) FNVBOXDISPIFWDDM_ADAPTEROP(PCVBOXDISPIF pIf, D3DKMT_HANDLE hAdapter, LPCWSTR pDevName, PVOID pContext);
+static DWORD vboxDispIfWDDMAdpHdcCreate(int iDisplay, HDC *phDc, DISPLAY_DEVICE *pDev)
+{
+    DWORD winEr = ERROR_INVALID_STATE;
+    memset(pDev, 0, sizeof (*pDev));
+    pDev->cb = sizeof (*pDev);
+
+    for (int i = 0; ; ++i)
+    {
+        if (EnumDisplayDevices(NULL, /* LPCTSTR lpDevice */ i, /* DWORD iDevNum */
+                pDev, 0 /* DWORD dwFlags*/))
+        {
+            if (i == iDisplay || (iDisplay < 0 && pDev->StateFlags & DISPLAY_DEVICE_PRIMARY_DEVICE))
+            {
+                HDC hDc = CreateDC(NULL, pDev->DeviceName, NULL, NULL);
+                if (hDc)
+                {
+                    *phDc = hDc;
+                    return NO_ERROR;
+                }
+                else
+                {
+                    winEr = GetLastError();
+                    Assert(0);
+                    break;
+                }
+            }
+        }
+        else
+        {
+            winEr = GetLastError();
+            Assert(0);
+            break;
+        }
+    }
+
+    return winEr;
+}
+
+
+typedef DECLCALLBACK(BOOLEAN) FNVBOXDISPIFWDDM_ADAPTEROP(PCVBOXDISPIF pIf, D3DKMT_HANDLE hAdapter, DISPLAY_DEVICE *pDev, PVOID pContext);
 typedef FNVBOXDISPIFWDDM_ADAPTEROP *PFNVBOXDISPIFWDDM_ADAPTEROP;
-static DWORD vboxDispIfWDDMAdapterOp(PCVBOXDISPIF pIf, LPCWSTR pDevName, PFNVBOXDISPIFWDDM_ADAPTEROP pfnOp, PVOID pContext)
-{
-    D3DKMT_OPENADAPTERFROMGDIDISPLAYNAME OpenAdapterData = {0};
-    wcsncpy(OpenAdapterData.DeviceName, pDevName, RT_ELEMENTS(OpenAdapterData.DeviceName) - 1 /* the last one is always \0 */);
-    DWORD err = NO_ERROR;
-    NTSTATUS Status = pIf->modeData.wddm.pfnD3DKMTOpenAdapterFromGdiDisplayName(&OpenAdapterData);
-    Assert(!Status);
-    if (!Status)
-    {
-        BOOLEAN bCloseAdapter = pfnOp(pIf, OpenAdapterData.hAdapter, OpenAdapterData.DeviceName, pContext);
-
-        if (bCloseAdapter)
-        {
-            D3DKMT_CLOSEADAPTER ClosaAdapterData = {0};
-            ClosaAdapterData.hAdapter = OpenAdapterData.hAdapter;
-            Status = pIf->modeData.wddm.pfnD3DKMTCloseAdapter(&ClosaAdapterData);
-            if (Status)
-            {
-                Log((__FUNCTION__": pfnD3DKMTCloseAdapter failed, Status (0x%x)\n", Status));
-                /* ignore */
-                Status = 0;
-            }
-        }
-    }
-    else
-    {
-        Log((__FUNCTION__": pfnD3DKMTOpenAdapterFromGdiDisplayName failed, Status (0x%x)\n", Status));
-        err = ERROR_GEN_FAILURE;
+static DWORD vboxDispIfWDDMAdapterOp(PCVBOXDISPIF pIf, int iDisplay, PFNVBOXDISPIFWDDM_ADAPTEROP pfnOp, PVOID pContext)
+{
+    D3DKMT_OPENADAPTERFROMHDC OpenAdapterData = {0};
+    DISPLAY_DEVICE DDev;
+    DWORD err = vboxDispIfWDDMAdpHdcCreate(iDisplay, &OpenAdapterData.hDc, &DDev);
+    Assert(err == NO_ERROR);
+    if (err == NO_ERROR)
+    {
+        NTSTATUS Status = pIf->modeData.wddm.pfnD3DKMTOpenAdapterFromHdc(&OpenAdapterData);
+        Assert(!Status);
+        if (!Status)
+        {
+            BOOLEAN bCloseAdapter = pfnOp(pIf, OpenAdapterData.hAdapter, &DDev, pContext);
+
+            if (bCloseAdapter)
+            {
+                D3DKMT_CLOSEADAPTER ClosaAdapterData = {0};
+                ClosaAdapterData.hAdapter = OpenAdapterData.hAdapter;
+                Status = pIf->modeData.wddm.pfnD3DKMTCloseAdapter(&ClosaAdapterData);
+                if (Status)
+                {
+                    Log((__FUNCTION__": pfnD3DKMTCloseAdapter failed, Status (0x%x)\n", Status));
+                }
+            }
+        }
+        else
+        {
+            Log((__FUNCTION__": pfnD3DKMTOpenAdapterFromGdiDisplayName failed, Status (0x%x)\n", Status));
+            err = ERROR_GEN_FAILURE;
+        }
+
+        DeleteDC(OpenAdapterData.hDc);
     }
 
@@ -149,5 +192,5 @@
 } VBOXDISPIFWDDM_ESCAPEOP_CONTEXT, *PVBOXDISPIFWDDM_ESCAPEOP_CONTEXT;
 
-DECLCALLBACK(BOOLEAN) vboxDispIfEscapeWDDMOp(PCVBOXDISPIF pIf, D3DKMT_HANDLE hAdapter, LPCWSTR pDevName, PVOID pContext)
+DECLCALLBACK(BOOLEAN) vboxDispIfEscapeWDDMOp(PCVBOXDISPIF pIf, D3DKMT_HANDLE hAdapter, DISPLAY_DEVICE *pDev, PVOID pContext)
 {
     PVBOXDISPIFWDDM_ESCAPEOP_CONTEXT pCtx = (PVBOXDISPIFWDDM_ESCAPEOP_CONTEXT)pContext;
@@ -172,5 +215,5 @@
     Ctx.pEscape = pEscape;
     Ctx.cbData = cbData;
-    DWORD err = vboxDispIfWDDMAdapterOp(pIf, L"\\\\.\\DISPLAY1", vboxDispIfEscapeWDDMOp, &Ctx);
+    DWORD err = vboxDispIfWDDMAdapterOp(pIf, -1 /* iDisplay, -1 means primary */, vboxDispIfEscapeWDDMOp, &Ctx);
     if (err == NO_ERROR)
     {
@@ -198,5 +241,5 @@
 } VBOXDISPIFWDDM_RESIZEOP_CONTEXT, *PVBOXDISPIFWDDM_RESIZEOP_CONTEXT;
 
-DECLCALLBACK(BOOLEAN) vboxDispIfResizeWDDMOp(PCVBOXDISPIF pIf, D3DKMT_HANDLE hAdapter, LPCWSTR pDevName, PVOID pContext)
+DECLCALLBACK(BOOLEAN) vboxDispIfResizeWDDMOp(PCVBOXDISPIF pIf, D3DKMT_HANDLE hAdapter, DISPLAY_DEVICE *pDev, PVOID pContext)
 {
     PVBOXDISPIFWDDM_RESIZEOP_CONTEXT pCtx = (PVBOXDISPIFWDDM_RESIZEOP_CONTEXT)pContext;
@@ -237,5 +280,5 @@
     Ctx.Info.Height = Height;
     Ctx.Info.BitsPerPixel = BitsPerPixel;
-    DWORD err = vboxDispIfWDDMAdapterOp(pIf, L"\\\\.\\DISPLAY1", vboxDispIfResizeWDDMOp, &Ctx);
+    DWORD err = vboxDispIfWDDMAdapterOp(pIf, (int)Id, vboxDispIfResizeWDDMOp, &Ctx);
     if (err == NO_ERROR)
     {