EditorWindow.python_docs():

Instead of using Netscape through os.system(), use the new
        browser.open() function to load the documentation on the
        default browser.  On Windows, this will use the installed
        documentation if it exists, instead of hitting python.org.

Tools/idle/EditorWindow.py

@@ -6,6 +6,7 @@ import imp
 from Tkinter import *
 import tkSimpleDialog
 import tkMessageBox
+import browser
 import idlever
 import WindowList
 from IdleConf import idleconf
@@ -288,14 +289,16 @@ class EditorWindow:
         else:
             self.io.loadfile(helpfile)
 
-    # XXX Fix these for Windows
-    help_viewer = "netscape -remote 'openurl(%(url)s)' 2>/dev/null || " \
-                  "netscape %(url)s &"
     help_url = "http://www.python.org/doc/current/"
+    if sys.platform[:3] == "win":
+        fn = os.path.dirname(os.path.dirname(os.path.dirname(__file__)))
+        fn = os.path.join(fn, "Doc", "index.html")
+        if os.path.isfile(fn):
+            help_url = fn
+        del fn
 
     def python_docs(self, event=None):
-        cmd = self.help_viewer % {"url": self.help_url}
-        os.system(cmd)
+        browser.open(self.help_url)
 
     def select_all(self, event=None):
         self.text.tag_add("sel", "1.0", "end-1c")