The default behavior of WinPython regarding your machine configuration is to keep a low profile: no key is added to Windows registry, no shortcut is added to Windows start menu, and so on (unless you register your distribution).

Similarly, the environment variables are almost not affected by WinPython, except for the PATH environment variable which is modified at runtime by prepending and appending some required WinPython paths. But the original PATH contents are still there. This may cause conflict issues from time to time, hence the next section.

Since v2.7.5.1 and v3.3.2.1, it is possible to override any environment variable in WinPython at runtime using the new WinPython configuration file named winpython.ini and located in settings WinPython folder (or in your user profile directory if you have removed the settings folder).

Here is the template winpython.ini file which is created at runtime (if the file doesn't exist yet):

[debug]
state = disabled

[environment]
## <?> Uncomment lines to override environment variables
#PATH = 
#PYTHONPATH = 
#PYTHONSTARTUP = 

Overriding the PATH environment variable is quite simple:

[environment]
## <?> Uncomment lines to override environment variables
PATH = D:\foobar

That's it.

In addition all existing environment variables are available and the syntax allows using them with %VAR_NAME%. This allows, for instance, appending folder to the system path:

PATH = %PATH%;<MyFolderPath>;

The above will append <MyFolderPath> to the current system path.