Added a more truthful message about what really is wrong.

diff --git a/dlls/dsound/dsound_main.c b/dlls/dsound/dsound_main.c
index 2229112..b4cd763 100644
--- a/dlls/dsound/dsound_main.c
+++ b/dlls/dsound/dsound_main.c
@@ -1769,6 +1769,13 @@
 
 		return S_OK;
 	}
+#else
+	if ( IsEqualGUID( &IID_IDirectSound3DBuffer, riid ) ) {
+		FIXME("%s: I know about this GUID, but don't support it yet\n",
+		      debugstr_guid( riid ));
+		*ppobj = NULL;
+		return E_FAIL;
+	}
 #endif
 
         if ( IsEqualGUID( &IID_IDirectSound3DListener, riid ) ) {