Best would be to use the Firefox 45.6.0 esr version to have a release that is still supported with security updates in cases like that.

Firefox 45.6.0 ESR:

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

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

• https://support.mozilla.org/kb/your-hardware-no-longer-supported
• https://support.mozilla.org/kb/end-support-windows-xp-and-vista

The system requirements haven't changed between Firefox 47 and Firefox 50, so I'm not sure what's going wrong with the installer. Could you describe the problem in more detail?

If you are not going to use Firefox 50, you should consider using the "Extended Support Release" of Firefox 45, which at least is getting security updates. In a couple months, all Windows XP users will be switched from the regular releases to the ESR version of Firefox 52. So you could start early...

The installer from the ESR version of Firefox can be found here:

https://www.mozilla.org/firefox/organizations/all/

Some protection programs don't like the update/install stubs. Download Firefox For All languages And Systems {web link}

I'm running XP SP3 with a non SSE2 processor. Ver. 50 won't install with that processor. 47.0.2 (the version offered in the automatic update) won't install. Scrolls and eventually times out on the install.

Was trying to get the latest version before all versions (I understand after 48) require a new processor.

But the version you're running (43.0.4) also requires a "Pentium 4 or newer processor that supports SSE2". https://www.mozilla.org/firefox/43.0.4/system-requirements/

So maybe the problem with the installation is something else.

Firefox 48 should still work on XP and SSE

• http://download.cdn.mozilla.net/pub/firefox/releases/48.0.2/win32-sha1/en-US/

See also:

• Bug 1318913 - Version 49.0 would not work on my XP PC

From:

• https://www.mozilla.org/en-US/firefox/48.0.2/system-requirements/

To install Firefox on a Windows XP system, because of Windows restrictions, the user will have to download Firefox 43.0.1 and then update to the current release.

• https://www.mozilla.org/en-US/firefox/49.0/system-requirements/

Pentium 4 or newer processor that supports SSE2