Some of the newer ZA versions have been a bit problematic. I'm now using ZAP 6.1.744.001 which seems to have solved the earlier problem with the 6.* series. Of the earlier versions, 5.5.094.000 was probably the last stable one. See here.

For more complete discussion, you might want to take a look at the ZA forum here. (Look in the Installation, Uninstall, Upgrade section.)

farmer70acre

I assume you are using broadband
DSL?
Cable?
satellite?

Even with cable ISP, what I myself use at home is Avast
As far as I can tell, it does a good job.
The trouble might be its updates. When I "wiggle the mouse" to wake up my PC (with 1 GB RAM), the first thing that happens is the virus definition update, at the end of which a synthesized voice says "Virus database updated!"
That takes a little while even on cable so might be really annoying on your dial-up -- I don't know.
My reason for using Avast is that it has come to my rescue in many situations at work where I am the tech support person (higher education). I have used it and also sometimes AVG to get out of situations not totally handled by Symantec (Norton). I can usually count on Avast to find and take care of things that might not even come up in Norton. Part of how it does this initially is that once you finish downloading and installing, it asks whether you want a boot-time scan (Yes). Then when it finds something it shows the name in text and gives you numeric options, including "2" Delete the file (which is usually what I choose).
"Delete all" is an option but I usually want to see every one and not ride blind.
Avast is free "for home use" but uses a Registration key, which you just request and they email it to you.
I just copy and paste it into the registration blank because it is quite long. I have put ZA on but have uninstalled it and everything that works that way in favor of just Avast, which (my opinion) would be great for the dial-up (with the caveat about the update times). The best.

On cable I believe that is not an issue for me because my router / WiFi access point is also a firewall in hardware -- the SMC Barracade. We have been running it for more than a year with Windows XP and an iMac and to my knowledge nothing else was required at the house (residence).

I'm also using ZoneAlarm version 6.1.744.001 on my 8400 with dial-up and it works just fine. I think the trick is to turn off antiviral software before installing this version.

Ron