64-bit 3.5.0b4 works for me in Windows 7. Try loading _tkinter.pyd in [Dependency Walker][1]. Or try loading the dependent DLLs directly via ctypes:

    import os
    import _ctypes

    dlls_path = os.path.dirname(_ctypes.__file__)
    for d in ('tcl86t.dll', 'tk86t.dll'):
        path = os.path.join(dlls_path, d)
        try:
            _ctypes.LoadLibrary(path)
        except OSError:
            print('failed:', path)

[1]: http://dependencywalker.com