".url" files

I've many ".url" files on my HDD, and noticed that:
by exetute them, Firefox opens without load my profile.
BTW, if Firefox is already opened, the url loads as usual on new tab.

I think ".URL" are assigned to
"C:\Program files\Mozilla Firefox\App\Firefox\firefox.exe"
instead of
"C:\Program files\Mozilla Firefox\FirefoxPortable.exe"
, but on my XP I can't see a "Open with" option to redirect them.

Thanks for this great app, I use because it's easy to backup, so easy to keep crap/error free