The last available version of Mozilla Firefox that will run under Windows XP is version 52
WARNING - I will NOT be held responsible for any damages the software(s) and methods shown in this video may cause to yours or someone else's computer, hardware, software, and/or data, including loss of use of such devices and/or loss of data and/or loss of profits from the resulting inability to use such devices and data. Any information or program you choose to put into use from this video is done AT YOUR OWN RISK. As a precaution, I recommend backing up any irrecoverable data before installing and using ANY new software(s), including those shown in this video.
The last available version of the Mozilla Firefox web browser that will function under the Windows XP operating system is Mozilla Firefox version 52. This video will show you how to download and install the newest version of the Mozilla Firefox web browser, in a portable configuration, under the Windows XP OS.
Download link (elect to download the newest version of Mozilla Firefox ESR, Portable Edition 52):
https://sourceforge.net/projects/portableapps/files/Mozilla%20Firefox%2C%20Portable%20Ed./
If the first link does not lead you to where you wish to go, load the following link:
https://sourceforge.net/projects/portableapps/files/
and on the loaded page, hold CTRL and press F, then release these keys and type the following text: Firefox