XP does not stop working between updates, in the same way I can still run Windows 3.11 or 95 any time I like.
All of the current windows updates will still be available if you reinstall windows.
Over 90% of problems can be avoided by doing this 1st thing;
XP users only need to change the way they use the PC.
Create an admin profile and downgrade yours to a "limited user".
To install new software, you now have to right-click and run as admin.
Remove Java, and reinstall it only if you need it (you don't need Java to use Jscript in webpages).
Make sure Flash is up to date every week.
Do not use Internet Explorer. Use Opera or Firefox.
In a more secure browser, you can set plugins to run on demand.
You can just set Flash and Java to ask before running. It makes some sites more annoying, but more secure.
Do not use streaming sites that require you to install a "special" codec.
Avast is quite good, but very heavy on 32bit Windows. Stick with it, but make sure it is updating each day.
Install Windows Defender, update it, then disable runtime scanning and change the widows service to "manual" (keep it as a backup in case of disaster).
Install some security plugins in your browser, so you can see and test bad files and sites before anything reaches you (the less you give Avast to do, the better off you are).
I'll add a link to a useful collection at the bottom.
Upgrade your taskmanager to "Process Explorer" from the Microsoft site, as it shows more info if you need to look at what is running.
Make sure you use a more secure torrent program that has block-lists.
Finally do not blindly "open" files or links sent in an email.
"Save" the file to disk to be checked by your AV, and copy links to an online checker (like Virus Total).