Problem: you have 64-bit Python, and a 32-bit installer. This will cause problems for extension modules.
The reasons why the installer doesn’t finds Python is the transparent 32-bit emulation from Windows 7. 64-bit and 32-bit programs will write to different parts of the Windows registry.
This means that the 64-bit Python installer writes to
HKLM\SOFTWARE\Python, but the 32-bit setuptools installer looks at
HKLM\SOFTWARE\wow6432node\Python (this is handled by windows automatically, programs don’t notice). This is expected behavior and not a bug.
Usually, you have these choices:
- the “clean” way: use 32-bit Python if you have to use 32-bit modules or extensions
- the other “clean” way: only use 64-bit installers when using 64-bit Python (see below)
- what the answer above suggests: copy
HKLM\SOFTWARE\wow6432node\Python, but this will cause problems with binary distributions, as 64-bit Python can’t load 32-bit compiled modules (do NOT do this!)
- install pure Python modules with setuptools instead of the distutils installer (easy_install or pip)
For setuptools itself, for example, you can’t use a 32-bit installer for 64-bit Python as it includes binary files. But there’s a 64-bit installer at http://www.lfd.uci.edu/~gohlke/pythonlibs/ (has many installers for other modules too). Nowadays, many packages on PyPi have binary distributions, so you can install them via pip.