But not for many sites. My aunt's bank won't work with pre-Quantum
versions of Firefox. She has hit many sites that won't work with old
Firefox. Site requirements have continued to grow regarding minimum
features in Firefox. One, for example, is CSS may now compute
brightness rather than used fixed settings, and old versions of FF can't
handle that. Just because FF pre-Quantum "works" on XP doesn't equate
to FF working at sites. The last version of Firefox is 52.9ESR that
supports on XP, so you're using an older version than needed on XP.
That is the latest my aunt can get on your XP, and yet lots of sites
won't accept. Oh, and using about:config tweak or an extension to lie
about the User Agent string the webclient sends to the server won't work
anymore simply because that won't magically embue features that are only
available in later versions required by sites.
The longer you hang onto old versions of web browsers, the more sites
won't support them. The UA string trick won't work, anymore. They
moved forward and can demand features the old web browsers cannot
support. Although MyPal may help, as it did with my aunt, it is from a
fork from Pale Moon which is a fork from pre-Quantum Firefox, so both
Pale Moon and MyPal won't have the later features demanded by some
sites.
As for getting a newer Windows, you can get 10 for free. Just never
validate it. Leave it indefinitely in trial mode. You'll end up with a
watermark on the background, but there's a tweak to get rid of it. Some
tools aren't available, but most users don't use them, and they aren't
critical to using the OS. The trial version of Windows 10 never
expires.
Another suggestion by Easter is to use Linux on a USB stick, and boot
from that. You don't even have to unload Windows XP if you load Linux
in a VM (Virtual Machine). There are free VMMs (Virtual Machine
Managers), like VirtualBox and VMware Player. When you want to browse,
run the VMM on your host OS (Windows XP) and load the VM with the guest
OS (Mint seems close to Windows for new Linux users coming from
Windows), and use a new web browser along with the Webkit versions of
the add-ons.
As I recall, after installing VirtualBox on Windows, you followed by
installing the guest additions package to Virtualbox. That let it
better communicate the hardware from the host OS to the VM running the
guest OS. That was when I was running Windows as guest OSes. You'll
want a pre-6 version of VirtualBox to run on Windows XP. There's a
Virtualbox community (forum) to get help. The last time I used
Virtualbox, it had its own taskbar. So, you loaded Vbox as a startup
program, you'd see a toolbar (atop the Windows taskbar), and to start
programs inside the VM just had you click on the shortcuts in the VBox
toolbar. Made it rather transparent that you were using running those
programs inside a VM.
Instead of running Vbox on Windows XP, and use a newer OS to run a newer
web browser inside a VM, you could switch it around: boot into a newer
OS on which you run Vbox, and run your old XP inside a VM. There are
tools to create a VHD (Virtual Hard Disk) image of your current
partition (OS + apps) that you could load inside a VM. While my
recollection is of using a Vbox tool to create a VHD from your existing
partition(s), Microsoft (via SysInternals they acquired) has their own
Disk2VHD tool to do the same. Vbox and Vmware can load VHDs (.vhd
files) created by other tools. For example, I use Macrium Reflect Home
which can create a .vhd file as an image of my partitions (instead of
into their proprietary .mrimg files), that can be loaded by Vbox or
VMware Player. Once you image your current partition with Windows XP
and apps into a VHD file (I would also suggest saving an MRIMG file if
using Macrium), you could install a new OS onto those partition(s),
install Vbox or VMware Player, and load the .vhd file you created to
have your old Windows XP running inside a VM.
Just because your old horse can longer carry the full load doesn't mean
you can't tow along a young burro to handle part of the load.