[itimpi]

here is the patch to setup.py to use the INCLUDE environment variable if set, and otherwise use your old preset values:

@@ -412,11 +412,16 @@
                                   )
                  ]
     if iswindows:
+        sEnvInclude = os.environ.get('INCLUDE')
+        if sEnvInclude is None :
+            linclude_dirs=['C:/WinDDK/6001.18001/inc/api/',
+                          'C:/WinDDK/6001.18001/inc/crt/']
+        else:
+            linclude_dirs = sEnvInclude.split(';')
         ext_modules.append(Extension('calibre.plugins.winutil',
                 sources=['src/calibre/utils/windows/winutil.c'],
                 libraries=['shell32', 'setupapi'],
-                include_dirs=['C:/WinDDK/6001.18001/inc/api/',
-                              'C:/WinDDK/6001.18001/inc/crt/'],
+                include_dirs=linclude_dirs,
                 extra_compile_args=['/X']
                 ))
     if isosx:

Please feel free to recode more elegantly (which I am sure is possible).