Comment #5 on issue 613 by spielmann.robert: Using binary installer fails on 64 bit Windows
http://code.google.com/p/robotframework/issues/detail?id=613
I didn't test installation from source, but I tested this by generating a .exe installer, which works fine. Using the 32bit installer with 64bit Python is definitely impossible because the required registry entries are different between 32bit and 64bit versions of Python.
