Index: /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/common/VBoxMPUtils.cpp
===================================================================
--- /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/common/VBoxMPUtils.cpp	(revision 46850)
+++ /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/common/VBoxMPUtils.cpp	(revision 46851)
@@ -62,5 +62,7 @@
     if(major == 6)
     {
-        if (minor == 2)
+        if (minor == 3)
+            s_WinVersion = WIN8_1;
+        else if (minor == 2)
             s_WinVersion = WIN8;
         else if (minor == 1)
Index: /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/common/VBoxMPUtils.h
===================================================================
--- /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/common/VBoxMPUtils.h	(revision 46850)
+++ /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/common/VBoxMPUtils.h	(revision 46851)
@@ -94,5 +94,6 @@
     WINVISTA  = 4,
     WIN7      = 5,
-    WIN8      = 6
+    WIN8      = 6,
+    WIN8_1    = 7
 } vboxWinVersion_t;
 
Index: /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/common/VBoxMPVidModes.cpp
===================================================================
--- /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/common/VBoxMPVidModes.cpp	(revision 46850)
+++ /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/common/VBoxMPVidModes.cpp	(revision 46851)
@@ -357,5 +357,5 @@
                      * if the framebuffer window requires scrolling to fit the guest resolution.
                      * So add 1024x768 resolution for win8 guest to allow user switch to it */
-                    (VBoxQueryWinVersion() != WIN8 || resolutionMatrix[resIndex].xRes != 1024 || resolutionMatrix[resIndex].yRes != 768) &&
+                    ((VBoxQueryWinVersion() != WIN8 && VBoxQueryWinVersion() != WIN8_1) || resolutionMatrix[resIndex].xRes != 1024 || resolutionMatrix[resIndex].yRes != 768) &&
 #endif
                     !VBoxLikesVideoMode(iDisplay, resolutionMatrix[resIndex].xRes, resolutionMatrix[resIndex].yRes - yOffset, bitsPerPixel))
Index: /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/wddm/VBoxMPMisc.cpp
===================================================================
--- /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/wddm/VBoxMPMisc.cpp	(revision 46850)
+++ /trunk/src/VBox/Additions/WINNT/Graphics/Video/mp/wddm/VBoxMPMisc.cpp	(revision 46851)
@@ -619,5 +619,5 @@
     else
     {
-        Assert(ver == WIN7 || ver == WIN8);
+        Assert(ver == WIN7 || ver == WIN8 || ver == WIN8_1);
         pKeyPrefix = VBOXWDDM_REG_DISPLAYSETTINGSKEY_PREFIX_WIN7;
         cbKeyPrefix = sizeof (VBOXWDDM_REG_DISPLAYSETTINGSKEY_PREFIX_WIN7);