I ran what you said. Here's what I got.

C:\Python34>c:\python34\python.exe -m idlelib.idle
Traceback (most recent call last):
  File "c:\python34\lib\runpy.py", line 170, in _run_module_as_main
    "__main__", mod_spec)
  File "c:\python34\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "c:\python34\lib\idlelib\idle.py", line 10, in <module>
    import idlelib.PyShell
  File "c:\python34\lib\idlelib\PyShell.py", line 29, in <module>
    from idlelib.EditorWindow import EditorWindow, fixwordbreaks
  File "c:\python34\lib\idlelib\EditorWindow.py", line 22, in <module>
    from idlelib.configHandler import idleConf
  File "c:\python34\lib\idlelib\configHandler.py", line 703, in <module>
    idleConf=IdleConf()
  File "c:\python34\lib\idlelib\configHandler.py", line 171, in __init__
    self.LoadCfgFiles()
  File "c:\python34\lib\idlelib\configHandler.py", line 694, in LoadCfgFiles
    self.userCfg[key].Load() #same keys
  File "c:\python34\lib\idlelib\configHandler.py", line 68, in Load
    self.read(self.file)
  File "c:\python34\lib\configparser.py", line 672, in read
    self._read(fp, filename)
  File "c:\python34\lib\configparser.py", line 1058, in _read
    raise MissingSectionHeaderError(fpname, lineno, line)
configparser.MissingSectionHeaderError: File contains no section headers.
file: 'C:\\Users\\Tomk\\.idlerc\\config-extensions.cfg', line: 1
'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x0
0\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'

________________________________
 From: SilentGhost <report@bugs.python.org>
To: t.kember1@btinternet.com 
Sent: Sunday, 13 July 2014, 13:15
Subject: [issue21973] Can't use Idle

SilentGhost added the comment:

This is the normal content of idle.bat
Could you run `c:\python34\python.exe -m idlelib.idle` from the command-line and post the output here?

----------
components: +IDLE
nosy: +SilentGhost, kbk, roger.serwy, terry.reedy

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Python tracker <report@bugs.python.org>
<http://bugs.python.org/issue21973>
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