from http://howagain.com/create-a-portable-firefox-and-run-multiple-profiles-or-versions/
This Howto was created by C.Taylor at Howagain.com. I take no credit for the content.
This is just a list of distilled steps to clarify the instructions. For detailed instructions, view the original article at: (http://howagain.com/create-a-portable-firefox-and-run-multiple-profiles-or-versions/)
https://www.mozilla.org/en-US/firefox/all/
- (Make sure to get offline version)
 
- Locate Firefox executable under 'core' directory
 - Remove the setup.exe file
 - Make shortcut to firefox executable
 
- 
Change shortcut properties target string - append:
-no-remote –profile “main” - 
Rename shortcut to match profile name
 
- Run firefox, and install any extensions or profile changes you want:
 - These changes will now be saved under a profile folder called "main"
 - These changes will be across all profiles. (Save minute per-profile settings for the individual profiles)
 
- Make a copy of the 'main' folder for as many profiles as needed
 - Rename each "main" copy to exactly match the name of the profile you'll create
 
- Change each shortcut settings to the appropriate profile name
 
- Install scripts and extensions, etc.
 
- Run firefox from your profile-specific shortcuts