ImportError：无法导入名称别名

我刚刚在Windows Vista上使用官方站点的安装程序安装了Python 2.7.1，运行python.exe时得到这样的错误

C:\Python27>python.exe Traceback (most recent call last): File "C:\Python27\Lib\site.py", line 553, in <module> main() File "C:\Python27\Lib\site.py", line 542, in main aliasmbcs() File "C:\Python27\Lib\site.py", line 467, in aliasmbcs import locale, codecs File "C:\Python27\Lib\locale.py", line 15, in <module> import encodings File "C:\Python27\Lib\encodings\__init__.py", line 32, in <module> from encodings import aliases ImportError: cannot import name aliases 

与Python 3.1.3，也刚刚安装

 Fatal Python error: Py_Initialize: can't initialize sys standard streams Traceback (most recent call last): File "C:\Python31\lib\encodings\__init__.py", line 32, in <module> ImportError: cannot import name aliases This application has requested the Runtime to terminate it in an unusual way. Please contact the application's support team for more information. 

到底是怎么回事？ 我应该configurationPYTHONPATH还是这样的？ 如果是这样，它应该具有什么样的价值？