For starters here are some basic Free software programs that work good for windows xp, That are helpful for speeding up and protecting your computer
Some Anti Virus Software that works.
At this current time early 2018 there are really only three low cost free Anti Virus programs that seem to run stable on Windows XP 32bit service pack 3 systems. The first being Avast which is a good basic program basically one button use, best for basic users but can be a bit heavy on resources. The next is 360 Total Security which is a great low resource anti virus system works on 32 bit systems has a fairly complete suite and takes less than 100mb of resources memory and cpu usage making about the lightest and fastest of the good programs. The last is the current version of Kaspesky which is fairly fast and more comprehensive but less user friendly it may take some tweaking and moderate user level setup to function well. Before installing any of these you need to completely uninstall any anti virus programs still on your computer for most you will need to download the uninstall program from the software publishers site as a simple uninstall using Windows will not completely remove anti virus programs. Two sites that have some pretty good guides and info on removing Anti virus programs are pchell.com and bleepingcomputer.com .
Programs for cleaning up your computer.
Most of the software on the internet for cleaning up and possibly speeding up older PC's is total junk. Users should avoid nearly any software advertised to easily speed up fix you PC. Yet there are a few good programs out there for free that can help. One of the best is ccleaner which is a basic cleaner and registry editor it also includes a nice startup editor for minimizing the programs that auto start load when you turn on your computer. Next is Malewarebytes one of the best basic anti virus removal tools on the market that can help remove most maleware. Another helpful tool for cleanup is Rkill which stops potential unwanted programs from running so they can be deleted or fixed.