Hi noobs! All versions are listed here: https://ftp.mozilla.org/pub/mozilla.org/firefox/releases/ Look for the version number (in your case 6.0.2) and then search in its subfolders for the right operating system. Well, probably it's a bit too tricky, so in your case it should be either https://ftp.mozilla.org/pub/mozilla.org/firefox/releases/6.0.2/win32/ (for any '''Windows''') or even more likely https://ftp.mozilla.org/pub/mozilla.org/firefox/releases/6.0.2/mac/ (for any '''Apple''', i.e. like OSX). Then select by the country codes, i.e. 'en-US' for US-English and download the .exe (Windows) / .dmg (Apple) - file. In Windows, just run the executable of the downloaded Firefox version , it will check for a previously installed version (in your case 7.01) and keeps your profile (bookmarks, passwords etc.). For Mac it should be the same routine, too lazy to test right now. Then make a fresh new install from the .exe/.dmg file. Have fun ;) Anyway, since i don't know how to perform a parallel install of Firefox: for security reasons you should always keep the latest version running on your system!!! If you '''have''' to downgrade, only to run a single other program, consider this great deal: go and install another browser for this task. IE, chrome, iceweasel...u name it. If it has to be Firefox, at least use another up-to-date browser for that period of time. Use it for '''ALL''' the other stuff you do on the web to stay 'safe', you never know what might happen.