Unregistering Firefox Portable 65

I've been using Firefox Portable 65 for awhile and just went to Firefox Portable 72. It works perfectly except I can't seem to open links in 72 - it still wants to use Portable 65. I have tried changing the fle associations to 72 and it still opens 65. They are in two separate folders. I don't want to use 65 but I don't want to totally delete it. How can I unregister it for urls and html and so on and have 72 open them instead? Firefox defaults are grayed out in Windows (7) default programs and are all on my old Firefox 56 (desktop type) that I use from time to time. I just need Windows to forget about 65. Thank you for any help