@ OrangeCrate
I generally don't like recommending Old versions of Security software, especially if the updates were security related, rather than adding more bells and whistles, unfortunately it is many years since I used ZA.
For me some of these issued that were fixed may have improved things rather than just bells and whistles.
New and improved features in ZoneAlarm version 6.1.744.000
* Fixed - Service stability issue
* Fixed - Communicate with the centralized server issue
* Fixed - Overlapped text in support and update information
* Fixed - Various other bug fixes
New and improved features in ZoneAlarm version 6.1.737.000
* Fixed - Compatibility issues with Adaptec USB driver
* Fixed - Nortel VPN can not connect
* Fixed - Compatibility issue when System Mechanic Startup Guard is enabled
* Fixed - PdaNet can't connect
* Fixed - VSNET 2003 issues
* Fixed - TrueVector application error in event viewer log
* Fixed - High vsmon CPU usage
* Fixed - "Deny" Button in program alert pushed off the edge
* Fixed - Icons lost in program list after upgrade
* Fixed - PC Cillin 2006 issue
* Fixed - System stability issues
* Fixed - Various other bug fixes
New and improved features in ZoneAlarm Antivirus version 6.0.667.000
* Fixed - POP email not working when co-existing with NAV
* Fixed - Free ZA blocking some Remote access software from accessing ZA Alert notifications
* Fixed - Propel compatibility issue
* Fixed - Multiple 'loopback' entries in firewall zones after upgrade
New and improved features in ZoneAlarm Antivirus version 6.0.631.003
* Fixed network detection issue.
New and improved features in ZoneAlarm version 6.0.631.002
* Routine maintenance items
Thanks Bob, my concerns were also if it is compatible for older OSes as I couldn't find a system requirements on the PCTools site