I do a fresh install of Windows every 9-12 months. Things just get gummed up after a while. Software I needed once then forgot about, leftover folders that uninstallers missed, caches and Windows update installation files and other things filling up my system drive. Context menus become unruly, startup programs need to be monitored... It's just a lot easier to wipe the slate clean every once in a while than try to manage it all. And doing an upgrade in place doesn't accomplish any of this.
I do this with all my devices - my laptop, my phone, my iPad... It's nice setting things up from scratch now and then.
The Environmental Variable trick is good to know, but it's just as easy to use a symlink to redirect Calibre to the folder of my choice if I decide to use the regular installer. But even that's an extra step I can do without.
Now, I could call out the config folder from the command line when starting Calibre,
then we would be on to something. I always launch Calibre from my file manager, and I could build that right in.
But in the meantime, the portable version continues to work fine for helping me to manage my small collection of ebooks
