I have Firefox installed and despite closing it and opening Firefox Portable when I click on a pdf for example or an html file it opens the installed firefox instead of the portable one. I have not set "Multiple Instances" to true and I understand that being it disabled is the default. Do note I have updated the portable "installation" to the latest portable release.
Edit: forgot to add I'm running it in W7 x64.
Use this tool to make Firefox Portable by default on windows Register Firefox Portable
Portabilizing application... 14 at the moment
But what in the case that I use a different FF portable version? such as a developer edition. should i install the regular then your fix again for the developer one? Also I use firefox from my pendrive. Well if this behavior is intended then yes I will use your suggestion.