hi jim, could you be more specific about what "won't work" means in regards to firefox 50 - do you get a particular error message or what else is wrong?

Thanks for your reply Philipp. I get an error message saying system is not able to load program. This started right after the new 50.0 was released. I read that Windows xp had to load with 43.0 then work up to 50. I removed Firefox form my files thinking it was corrupt. When trying to reinstall, I get the above message about starting with 43.0.1. Thanks for your help. Jim

can you give us a screenshot of that error message? How do I create a screenshot of my problem?

the updating from 43.0.1 is a thing of the past - since firefox 49 the installers offered to xp users on the download site should work fine as well - apart from the problem that you're describing and that we should troubleshoot now...

Install an older version of Firefox {web link} Look for the directory of the version that you want. But remember that old versions may have security issues.

Not at that computer at this time. Will get to it tonight. As I said I deleted Firefox on this computer and now can not reinstall. I have other computers that seem to work ok. However, I noticed when I went to these other computers then to "Help" and clicked on "About Firefox" I saw the version number 42.0. The system began to update and when finished it asked me to restart Firefox. I know the current version is 50.0 so when Firefox came back up, I looked at About Firefox again and saw version 43.0. I repeated the update process and got 45.0.2 then 47.0.2 then 50.0.

So I do not know why my primary computer will not allow me to reload Firefox. As stated the message says I need to install 43.0 first them I guess work it up to 50.0

Well one of my kids computer with Firefox would only go to version 48.0.2. Message said it could not go any further with updating. This suggest that 42 or 43 allowed my primary computer to function. How do I re-install the older version.?To at least try to see if it will install. Granted my computers are old but if I can keep them working I will.Do not want to spend money if I do not have to.

Firefox Release setups from versions 43.0.2 to 48.0.2 were signed in a way that WinXP SP2 users could not install. Since it was not possible to tell if the WinXP user has SP2 or SP3 installed the 43.0.1 was served so they could then update to current Release from. WinXP SP2 users can run the Firefox setups again starting 49.0 and later including 50.0

Thanks James. Now how can I re-install Firefox with the 42 0r 43 version?

The message I get when trying to down load Firefox on my Windows XP- "This version of Firefox requires a processor with SSE2 support." My computer had been working with Firefox, so what has changed and can I get it back? I know I will have to settle for at least the 43.0 version. And how do I find the version? Thanks for your help. Jim

thanks jim, so you should be able to download firefox 43 from Install an older version of Firefox under the link for xp sp2 users. you can then let the version automatically update till firefox 48 - this was the last version that supported older processors without sse2 support unfortunately...

Your hardware is no longer supported

Philipp, I tried but the system did not connect. So typed in : https://download-installer.cdn.mozilla,net/pud and was able to get to a site that gave me : win32-1.861-stab-installer.exe and I got it to load on my computer. It does have some funtionality but I can not get Live.com for my mail. Now, how do I "walk" this up to version 43 etc.? Thanks. Jim

Philipp, I figured it out. I now have version 43 back on my computer.As a recap, I am working with an old windows 95 unit that has been upgraded over the years to Windows XP. When Bill decided to "kill off the old" , I kept making mine work. I paid 2K for the damn thing and do not want to do that again. So when XP was rendered useless, I came to Firefox (THANK YOU!). I was not abe to get on the internet or email. So when I had Firefox working then lost it due to the 50.0 rollout, I was dead in the water. After getting involved seeing what happend, I was able to get on 1.8.. I then had Internet! From there, after trying several attemps to get to the Revised releases, I jused Googled :Firefox 43.0 release. AND Damn it worked. Thanks for your support. Jim