diff --git a/panda/src/dxgsg/Sources.pp b/panda/src/dxgsg/Sources.pp
index 92cc59b837..0b2655eb09 100644
--- a/panda/src/dxgsg/Sources.pp
+++ b/panda/src/dxgsg/Sources.pp
@@ -12,11 +12,14 @@
     putil linmath sgraph mathutil pnmimage event
     
   #define COMBINED_SOURCES $[TARGET]_composite1.cxx     
-  
+
+  // need to install these due to external projects that link directly with libpandadx (bartop)  
   #define INSTALL_HEADERS \
     config_dxgsg.h dxGraphicsStateGuardian.I dxGraphicsStateGuardian.h \
     dxTextureContext.h dxGeomNodeContext.h dxGeomNodeContext.I
 
+  // build dxGraphicsStateGuardian separately since its so big
+  
   #define SOURCES \
     dxGraphicsStateGuardian.cxx dxSavedFrameBuffer.I dxSavedFrameBuffer.h $[INSTALL_HEADERS]
     
diff --git a/panda/src/dxgsg/dxGeomNodeContext.h b/panda/src/dxgsg/dxGeomNodeContext.h
index 31c7cf2ba3..345c212259 100644
--- a/panda/src/dxgsg/dxGeomNodeContext.h
+++ b/panda/src/dxgsg/dxGeomNodeContext.h
@@ -35,6 +35,10 @@
 #define D3D_OVERLOADS   //  get D3DVECTOR '+' operator, etc from d3dtypes.h
 #include <d3d.h>
 
+#if DIRECT3D_VERSION != 0x0700
+#error DX7 headers not available, you need to install MS Platform SDK!
+#endif
+
 typedef struct {
      DWORD nVerts;
      D3DPRIMITIVETYPE primtype;
diff --git a/panda/src/wdxdisplay/Sources.pp b/panda/src/wdxdisplay/Sources.pp
index d36219567d..767bcf8d6f 100644
--- a/panda/src/wdxdisplay/Sources.pp
+++ b/panda/src/wdxdisplay/Sources.pp
@@ -10,15 +10,19 @@
     dxgsg
     
   #define COMBINED_SOURCES $[TARGET]_composite1.cxx 
-    
-  #define SOURCES \
-    config_wdxdisplay.h wdxGraphicsPipe.h wdxGraphicsWindow.cxx wdxGraphicsWindow.h
+  
+  // need to install these due to external projects that link directly with libpandadx (bartop)    
+  #define INSTALL_HEADERS \
+    config_wdxdisplay.h wdxGraphicsPipe.h wdxGraphicsWindow.h
     
   #define INCLUDED_SOURCES \
     config_wdxdisplay.cxx wdxGraphicsPipe.cxx 
     
-  #define INSTALL_HEADERS \
-    config_wdxdisplay.h wdxGraphicsPipe.h wdxGraphicsWindow.h
+  // note SOURCES shoult NOT include INCLUDED_SOURCES, that would cause a double build
+  // SOURCES should be headers and separately-built cxx files
+  // build wdxGraphicsWindow.cxx separately since its big
+  
+  #define SOURCES wdxGraphicsWindow.cxx $[INSTALL_HEADERS]
     
 #end lib_target