permanently disabling proxy servers

Is there some way to permanently disable the proxy server option in XP?
I ask because I help the members of my church congregation when they run into computer problems. I freely admit I am not a computer expert, but I have been working with computers for many years (since 1968 actually) and have a fair understanding of how they operate.
Several times in the past couple of years people have come to me with virus infections and in almost every case the virus has hijacked their system by rerouting their browsers through a proxy server. I know how to remove this setting, and MalwareBytes is nearly always successful in killing the virus itself, but I wonder if there isn't some way to prevent it from happening in the first place.
I looked but did not see anything in Administrative Tools/Local Sevices - where I would suspect it to be.
Any ideas?