Since some months ago, about the time the latest version of ZoneAlarm Free came out, I had been unable to upgrade. After downloading the most recent version of Zone Alarm, when attempting to install, it kept giving me the message "this version of ZoneAlarm is not compatible with Windows 98 or windows ME versions." This confounded me, because I am using windows XT, not 98 or ME. To make a long story short, after trying just about everything I could think of and still having the same problem, I used "add/remove programs" (from Control Panel) to uninstall ZoneAlarm. After the partially successful uninstall, the directory C:\Windows\Program Files\Zone Labs\ still continued to exist, and included a total of 44 files in the branch of subdirectories. When I renamed that directory to something else and ran the installer again, all went smoothly.
Hope this will help anyone experiencing the same problem.
Operating System:Windows XP Home Edition
Product Name:ZoneAlarm (Free)