I have just removed Zonealarm from my laptop and installed the free 30 day trial of the pro version of Comodo, intending to take up an annual subscription.
I successfully installed Comodo after a tiresome unsinstall of ZoneAlarm (had to remove most of the files manually).
For a while Comodo worked fine, then I had a problem with the internet provider (the network went down for a day or so) and afterwards the network is shown as not-connected on the laptop and I cannot access the internet. Sometimes Comodo asks if another network is found; it doesn't make any difference if I say yes or no, the 'new' network will still not connect to my isp.
However, my laptop can dual-boot into another version of XP with the free version of Comodo installed (this was installed some months ago) and that accesses the internet without any problems so it is not a problem with the internet connection. I suspect I need to do something to make Comodo work with the network but I don't know what.