First, thanks for the review. This is very instructive for me and the code is clearer now.

I tested your reviewed version, and it work (Tested only on Windows x86, Python 3.4, Windows SDK 7.1 actually).

I did the following changes :

* Add many docstrings, and improve existing ones.
* Change some comments that was unclear.
* Move .NET Framework directory/version finders in "RegistryInfo", like others.
* Started to add support for the MSVC++14.0 standalone compiler. (Note that this is Work in progress). This also help me to find what fail in actual structure.
* Add "msvc9_" prefix to actual patch functions and unpatched dict for better readability.
* Add VCforPython27 alternative in _augment_exception for IA64 (Arch not supported by VCforPython27)
* Replace "lib_extra" and "sdk_extra" by more generic "ccpu_dir" and "tcpu_dir" functions (For better compatibility with MSVC++14)
* Changes some parts (like VSTools) for reduce line length, avoid repetitions and improve PEP8.
* Make "unique_everseen" and "lookup" private.


But, it is not finished, I need at least to do:

- Finish MSVC++14 support.
- Remove patch for "find_vcvarsall" for MSVC++9 ? (Now "query_vcvarsall" patch also support VC++ for Python 2.7)
- Make more tests with more compilers/platforms/Python combination.
- Check compatibility with MSVC++11 and 12.
- Rename the file in "msvc_support.py" ? (not MSVC9 only)
- Rename "RegistryInfo" ?
- Make compute_env a class ? for split subparts like you did it for "RegistryInfo" and "PlatformInfo"