hello michaelolive, firefox 3.5.3 had been released over 4 years ago, so a smooth update process that jumps that many version numbers cannot be guaranteed or even tested. if you are having issues with starting the new version, please try creating a new profile: Profile Manager - Create, remove or switch Firefox profiles

in case there are issue with the "Setup Stub".exe, try using the full installer that is available for your system at https://www.mozilla.org/firefox/all/

Thanks Philipp. I have started afresh with a new download of Firefox 24 but it still does not start. I have only the default profile installed. Perhaps I should have included that I am using Windows XP with an AMD64 processor in a Foxconn motherboard.

thanks for reporting back - is it possible to launch the profile manager and to create a fresh profile (like described in the article i've linked to above)?

Hello, also, be sure you have sp2 and above, because firefox (from 13.0 version and above) needs xp sp2 or sp3, see:

Firefox 24 System Requirements

Firefox no longer works with some versions of Windows XP

thank you

Hi My Windows XP is sp3 but Firefox still does even start up. I may have a problem somewhere else, but if not and Firefox 24 will not work, how far back in Firefox versions would I need to go? Where can I get earlier versions without going all the way back to 3.5.3? (Everything on my 6 year old PC works well on XP and I don't want to try and run a new Windows and run into compatibility problems) Thanks Michael