Ya know... I would probably be saying the same thing right now... but I kept at it. When I installed Avast, the default method... it installed everything it had. Bad move on their part, because it kept rendering my network unusable. I called their Premium Tech Support... and they basically told me XP is dead and I had better upgrade my OS. I told them I like XP, and I pay 30 people to use those 64bit windoze on 30 or so machines. I prefer XP. And so, if you want to use Avast on Windows XP, don't call the tech support.
What I did was select the custom Install option, and unselected everything. Then the installation went like it should have. There was a small problem getting new virus definitions, but I eventually got them. All in one night. They really are making it hard for us XP users.
I will say that I picked up 10 machine licenses for Avast for 34.98 I think. That's all Paypal is showing I paid.
Malwarebytes... would have cost $400 for 10 machines. They do not appear to have a phone number you can call, in the event you need to talk to someone in the company. Avast does. I called it even though I was using the Free product. (Sure they were $1/hour Filipinos, but they seem to have been trained.)