http://scons.tigris.org/issues/show_bug.cgi?id=2791

--- setup.py
+++ setup.py
@@ -325,7 +325,7 @@
                 self.copy_scons(src, scons_version_bat)
 
         # --- distutils copy/paste ---
-        if os.name == 'posix':
+        if hasattr(os, 'chmod'):
             # Set the executable bits (owner, group, and world) on
             # all the scripts we just installed.
             for file in self.get_outputs():