https://support.mozilla.org/en-US/kb/use-firefox-another-language Sorry to say that Firefox 52.9.0 ESR was the last to support the ancient EOL Windows XP (and Vista) as Firefox 53.0 and later has required Windows 7 at minimum to run. The Chromium, Chrome and Opera web browsers dropped support of the old EOL WinXP and Vista back in April 20'''16''' while Firefox 52.9.0esr was released back on June 26, 20'''18'''.