Why exactly? The OP has not expressed any concern about old Windows patches, and Firefox ESR 52 had no need for them because it was designed to work on XP. Supposing his Vista is NOT perfectly patched to April 2017 specifications, what then? Do you suggest downloading a custom ISO from some unknown party and reinstalling from scratch because Windows Update no longer supports Vista? Or do you painstakingly prepare a list of missing updates for manual installation from the catalog? Either way, he will still not have a secure OS for use in 2021, nor will he have any systemwide support for TLS 1.2 that might benefit a Chrome 49 user in 2021. (If the OP is curious about the latter, then he should ask.)...let us know if your Vista SP2 OS is patched to the end of extended support (11-Apr-2017)...