diff -r 51ac5f06dd04 Lib/test/test_genericpath.py
--- a/Lib/test/test_genericpath.py	Tue Jul 24 03:45:39 2012 -0700
+++ b/Lib/test/test_genericpath.py	Thu Jul 26 09:37:59 2012 +0900
@@ -311,6 +311,8 @@
 
     @unittest.skipIf(sys.platform == 'darwin',
         "Mac OS X denies the creation of a directory with an invalid utf8 name")
+    @unittest.skipIf(sys.platform == 'win32',
+        "Win32 can fail cwd() with invalid utf8 name")
     def test_nonascii_abspath(self):
         # Test non-ASCII, non-UTF8 bytes in the path.
         with warnings.catch_warnings():
diff -r 51ac5f06dd04 Lib/test/test_os.py
--- a/Lib/test/test_os.py	Tue Jul 24 03:45:39 2012 -0700
+++ b/Lib/test/test_os.py	Thu Jul 26 09:37:59 2012 +0900
@@ -28,7 +28,7 @@
     import threading
 except ImportError:
     threading = None
-from test.script_helper import assert_python_ok
+from test.script_helper import assert_python_ok, make_script, temp_dir
 
 with warnings.catch_warnings():
     warnings.simplefilter("ignore", DeprecationWarning)
@@ -1061,6 +1061,45 @@
     def test_chmod(self):
         self.assertRaises(WindowsError, os.chmod, support.TESTFN, 0)
 
+    def test_chdir_invalid_filename(self):
+        # In code pages such as cp932(Japanese ShiftJIS), decoding 
+        # ANSI file name in can be failed with UnicodeDecodeError.
+        # If such errors happens while building exception object,
+        # the UnicodeDecodeError should not hide original exception.
+        
+        batfile = """
+chcp 932
+{exe} {scriptname}
+chcp {codepage}
+"""
+
+        pyscript = r"""
+import os, sys
+with open(r"{outputfilename}", "w") as f:
+    try:
+        os.chdir(b'\xe7w\xf0')
+    except WindowsError:
+        f.write("ok")
+    except Exception as e:
+        f.write(repr(e))
+"""
+
+        with temp_dir() as script_dir:
+            outputfilename=os.path.join(script_dir, 'result')
+            scriptname = make_script(script_dir, 'test', 
+                    pyscript.format(outputfilename=outputfilename))
+                    
+            batname = os.path.join(script_dir, "test.bat")
+            with open(batname, "w") as f:
+                codepage = locale.getpreferredencoding()[2:]
+                f.write(
+                    batfile.format(exe=sys.executable, 
+                        scriptname=scriptname, codepage=codepage))
+
+            subprocess.call(batname, shell=True)
+            with open(outputfilename) as f:
+                self.assertEqual("ok", f.read())
+
 class TestInvalidFD(unittest.TestCase):
     singles = ["fchdir", "dup", "fdopen", "fdatasync", "fstat",
                "fstatvfs", "fsync", "tcgetpgrp", "ttyname"]
diff -r 51ac5f06dd04 Python/errors.c
--- a/Python/errors.c	Tue Jul 24 03:45:39 2012 -0700
+++ b/Python/errors.c	Thu Jul 26 09:37:59 2012 +0900
@@ -595,10 +595,24 @@
     int ierr,
     const char *filename)
 {
-    PyObject *name = filename ? PyUnicode_DecodeFSDefault(filename) : NULL;
-    PyObject *result = PyErr_SetExcFromWindowsErrWithFilenameObject(
-                                                  PyExc_WindowsError,
-                                                  ierr, name);
+    PyObject *name=NULL, *result=NULL;
+    if (filename) {
+        name = PyUnicode_DecodeFSDefault(filename);
+        if (!name) {
+            /* display byte object if failed to convert to Unicode */
+            PyObject *bytename = PyBytes_FromString(filename);
+            if (bytename) {
+                name = PyObject_Repr(bytename);
+                Py_XDECREF(bytename);
+            }
+        }
+        /* Clear exception raised while constructing file name */
+        PyErr_Clear();
+    }
+    
+    result = PyErr_SetExcFromWindowsErrWithFilenameObject(
+                                        PyExc_WindowsError,
+                                        ierr, name);
     Py_XDECREF(name);
     return result;
 }