I'm reinstalling Python, on Windows 7, and one of the first dialog boxes is the Customize Python screen.

The default setting for "Add Python.exe to Path" is "Entire feature will be unavailable."

I always change this to "Will be installed on local hard drive."

It's not an issue, changing the system environment variables is a snap, but is there any upside to leaving this un-ticked?

If you only have one version of Python installed, it won't matter.

If you have multiple versions installed, then the first one that appears in your system Path will be executed when you use the "python" command. Additionally, it can make older versions inaccessible without extra work. For example, I had a system with Python 2.7 installed and I added 3.2 on top of that and checked the option to to add Python.exe to the path during installation. After doing that, entering both "python" and "python3" on the command line opened up Python 3.2, so I would need to enter the full path to the 2.7 interpreter when I needed to execute 2.x scripts.