How To Run Two Different Versions of Mozilla Firefox.
- Download Firefox 2.0.20 installer: http://www.oldapps.com/firefox.php?old_firefox=7
- Copy these instructions into text editor, and then close all open Firefox instances.
- Run “Custom” version of Firefox 2.x installer and choose the ultimate installation directory to be something like C:\Program Files\Mozilla Firefox 2.x, do not install any shortcuts (otherwise they will overwrite your other Firefox installation’s shortcuts), and do not start Firefox at the end of installation, just close installer when it is done.
- Open a command prompt and start the Firefox ProfileManager: C:\Program Files\Mozilla Firefox 2.x\firefox.exe -ProfileManager
- Create a new profile for your older version of Firefox (e.g., firefox_2.x_profile).
- Rename the newly created profile something meaningful (e.g., firefox_2.x_profile), and then close the Firefox ProfileManager.
- Use whichever version of Firefox you want by clicking the respective shortcut. Please note that you will not be able to open multiple windows of either version by repeatedly clicking the same shortcut. If you do this you will see an error message that says: “Firefox is already running, but is not responding. To open a new Window you must first close the existing Firefox process, or restart your system.” Instead, to open another window of the same version, just click on an already-open window of that version, and click
+ N, which will launch a new window from the existing process. A little-less convenient than click on the shortcut, but not too bad.