All versions of Firefox can be found on http://ftp.mozilla.org/pub/firefox/releases

Firefox 38 http://ftp.mozilla.org/pub/firefox/releases/38.0/win32/en-US/

You can consider to install the Firefox 38 ESR version as a custom install and create a separate profile or this version. Firefox 38.2.1/ ESR:

• https://www.mozilla.org/en-US/firefox/organizations/all/

• https://www.mozilla.org/en-US/firefox/38.2.1/releasenotes/
• https://www.mozilla.org/en-US/firefox/organizations/system-requirements/

You can install a portable (ESR) Firefox version to access websites that do not work with the current Firefox release. The portable version comes with its own profile folder and doesn't interfere with the currently installed release version.

• http://portableapps.com/apps/internet/firefox_portable
• http://portableapps.com/apps/internet/firefox-portable-esr

Thank you for the help.. This resolved my issues..

The Firefox 38 ESR has security fixes that the old 38.0 Release does not have. The 38.2.0 was Released when 40.0 came out and when Firefox 41.0 is released the ESR will be 38.3.0.

I see you selected the first reply as the solution. This is not a good idea as the old Firefox 38.0 Release is behind on security fixes while the Fx 38 ESR has security fixes since.

https://www.mozilla.org/security/known-vulnerabilities/