Maybe install it on a different drive. Here is the link Though, If that is what your asking. (http://ftp.mozilla.org/pub/mozilla.org/firefox/releases/24.8.1esr/win32/en-US/)

Hello, please note that the latest esr version is 31.4.0 you can download from the next link : https://www.mozilla.org/en-US/firefox/organizations/all/ older versions are vulnerable and unsupported. The ultimate guide to use multiple Channels of Firefox is from '''the-edmeister''', you can read it, please carefully in the next link : [http://forums.mozillazine.org/viewtopic.php?f=23&t=2821799 Using Release, ESR, Beta, Aurora, and/or Nightly together] thank you

You can install multiple Firefox versions via a custom install in different installation folders and only use the older Firefox version when you really need it for websites that do not work with the current release. * https://support.mozilla.com/kb/Custom+installation+of+Firefox+on+Windows *http://download.cdn.mozilla.net/pub/mozilla.org/firefox/releases/24.8.1esr/ Make sure not to start Firefox after the installation has finished and use the Profile Manager to create a new (separate) profile for each version. See: *https://developer.mozilla.org/Mozilla/Multiple_Firefox_Profiles *http://kb.mozillazine.org/Creating_a_new_Firefox_profile_on_Windows *http://kb.mozillazine.org/Shortcut_to_a_specific_profile You can add -no-remote to the command line to open another Firefox instance with its own profile and run multiple Firefox instances simultaneously. *http://kb.mozillazine.org/Opening_a_new_instance_of_Firefox_with_another_profile