On Windows your profile folder is in %APPDATA%\Mozilla\Firefox\Profiles\. This step can be skipped, although aside from protecting data, it's helpful to be able to refer to the original directory structure later. They are for Windows, although the real key to starting Firefox after the change (adding -allow-downgrade to your startup shortcut) is the same for Linux. These are instructions to install the version of Firefox you want and keep it that version, while also keeping your user profile intact.
