Index: /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UIMachineMenuBar.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UIMachineMenuBar.cpp	(revision 50041)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UIMachineMenuBar.cpp	(revision 50042)
@@ -473,4 +473,6 @@
     {
         pMenu->addAction(gActionPool->action(UIActionIndexRuntime_Toggle_VRDEServer));
+        if (!m_pSession->isExtensionPackUsable())
+            gActionPool->action(UIActionIndexRuntime_Toggle_VRDEServer)->setEnabled(false);
         fSeparator2 = true;
     }
Index: /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UISession.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UISession.cpp	(revision 50041)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UISession.cpp	(revision 50042)
@@ -77,4 +77,6 @@
 #include "CSnapshot.h"
 #include "CMedium.h"
+#include "CExtPack.h"
+#include "CExtPackManager.h"
 
 #ifdef VBOX_GUI_WITH_KEYS_RESET_HANDLER
@@ -128,4 +130,5 @@
     , m_machineStatePrevious(KMachineState_Null)
     , m_machineState(session().GetMachine().GetState())
+    , m_fIsExtensionPackUsable(false)
     , m_requestedVisualStateType(UIVisualStateType_Invalid)
 #ifdef Q_WS_WIN
@@ -1107,4 +1110,8 @@
     /* Load extra-data settings: */
     {
+        /* Extension pack stuff: */
+        CExtPack extPack = vboxGlobal().virtualBox().GetExtensionPackManager().Find(GUI_ExtPackName);
+        m_fIsExtensionPackUsable = !extPack.isNull() && extPack.GetUsable();
+
         /* Runtime menu settings: */
 #ifdef Q_WS_MAC
Index: /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UISession.h
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UISession.h	(revision 50041)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/runtime/UISession.h	(revision 50042)
@@ -94,4 +94,10 @@
     QCursor cursor() const { return m_cursor; }
 
+    /** @name Extension Pack stuff.
+     ** @{ */
+    /** Determines whether extension pack installed and usable. */
+    bool isExtensionPackUsable() const { return m_fIsExtensionPackUsable; }
+    /** @} */
+
     /** @name Runtime menus configuration stuff.
      ** @{ */
@@ -333,4 +339,10 @@
     QCursor m_cursor;
 
+    /** @name Extension Pack variables.
+     ** @{ */
+    /** Determines whether extension pack installed and usable. */
+    bool m_fIsExtensionPackUsable;
+    /** @} */
+
     /** @name Runtime menus configuration variables.
      ** @{ */
Index: /trunk/src/VBox/Frontends/VirtualBox/src/settings/machine/UIMachineSettingsDisplay.cpp
===================================================================
--- /trunk/src/VBox/Frontends/VirtualBox/src/settings/machine/UIMachineSettingsDisplay.cpp	(revision 50041)
+++ /trunk/src/VBox/Frontends/VirtualBox/src/settings/machine/UIMachineSettingsDisplay.cpp	(revision 50042)
@@ -399,7 +399,7 @@
                                  "Please install the Extension Pack from the VirtualBox download site as "
                                  "otherwise your VM will be started with Remote Display disabled.")
-                                .arg(GUI_ExtPackName);
+                                 .arg(GUI_ExtPackName);
         }
-#endif
+#endif VBOX_WITH_EXTPACK
 
         /* Check VRDE server port: */