Isn't this sufficient ?

!msconfig.exe

or this ?
https://github.com/winpython/winpython/wiki/Installation#Registration

What would one do inside msconfig? I just see boot options and such.

Registering from the Control Panel is also not working as it should. I don't see the files being associated correctly. Note that I have previously installed then uninstalled both Python(x,y) and Anaconda distributions.

Well, I never tried this functionnality on me. It's curious it doesn't work, as Pierre Raybaut said it was and I don't think I touched it.

This part is written in chinese, I don't have a clue on what the problem could be

https://github.com/winpython/winpython/blob/master/winpython/associate.py

I understand indirectly here that it works on some PCs
https://sourceforge.net/p/winpython/tickets/125/

I seem to have gotten the distribution to register from a Python interpreter:

>>> import sys
>>> from winpython import associate
>>> associate.register(sys.prefix)
Registered: Python

I now see the Windows Explorer context menu items for editing with IDLE and Spyder, so that's some progress. At least the winpython.associate module seems to work.

This was discussed before and the original author (Pierre) indicated it was included starting with "[r4c7a90c40f0a]". The solution devised in that ticket was not to modify winpython registration, but add another option entirely: 'Add/remove from system path'. Perhaps it was reverted as some point, because I don't see that feature in 2.7.6.4.

The functionality described in ticket 125 is interesting but appears to be missing from the python distro currently in Winpython. It's probably wrapped up in the Windows Installer, not core python itself. Since the goal is more transparent system integration, though, it's not really compatible with the hands-off nature of WinPython.

@petebachant if previous versions have been installed on a Windows machine, the associative registry entry may have an outdated path. This particular registry key is created by Windows when it first encounters a new executable file name so (re)installing won't fix anything.

If you have ever selected an application in the Open With... dialog, pressed OK, and been greeted with no activity, this broken-key-path error has manifested. LibreOffice, for instance, includes a version number in the installation directory path so LO apps fall prey to this problem after major upgrades.

1. Launch regedit and position the cursor at the top (My Computer)
2. Search for keys (not values or data) named python.exe and pythonw.exe; select the first instance which should be under HKEY_CLASSES_ROOT\Applications.
3. Check the data of the default value within the shell\open\command subkey: if the path is outdated, delete the key (the whole python.exe node) and it will be re-created with the correct path next time python.exe is run.

There are several other keys named after the executable but, in my experience, deleting the key under HKEY_CLASSES_ROOT will cause all other instances to be updated/recreated.

in the WinPython Control Panel you can register/unregister the base Python.