bently, I am sure you will get all kinds of answers to your question. Like you I have had no problem running XP firewall and ZoneAlarm Free at the same time using XP SP-1. No experience with SP-2 yet. My opinion would be to use whatever works without problems; however, I serriously doubt running two firewalls will add additional security. I prefer ZoneAlarm because it checks outgoing as well as incoming.

Best of luck!