CA used to offer a great free AV program, InnoculateIT. I used it for a long time until they discontinued support for it when virus technology exceeded the abilities of the basic program. If you don't already have good AV software, I would trust the quality of their product. They also have a great
Virus Information Center which includes links to search their Virus Encyclopedia. If you're ever stuck looking for virus info, and you can't find it on Norton or other sites, check CA.
Zone Alarm is another story. I use Zone Alarm ver. 2.6.362, which I believe is the last good version. Versions 3.xx absolutely suck for several reasons:
1. The uninstall program does NOT work. It causes "missing vxd" and "missing dll" errors that require skillful registry editing, just to get back where you started before the installation.
2. They went for a soft "touchy-squishy-feely" look that uses more resources to provide less information than the older version. My current version reports the IP address, the port from which it was sent, and the port it tried to hit on my machine for every hit. The info is available on screen when I want it. To get the same info from ZA 3.xx, I had to scroll through a mountain of logged info.
3. I've read far too many reports that it is a resource hog and causes many other problems.
I don't know about ZA 4.5, but for now, I trust my old version which I have installed on everything from Win 95 to XP Pro with no problems, either in operation or, when necessary, uninstalling.