Zone Alarm is bloatware and a real resource hog.

Kerio is OK
Agnitum is OK
If you can find a version of the long obsolete Tiny Personal Firewall it is very intuitive in use and uses virtually no resources. I am currently using up a free period of McAfee on my other computer and when it expires I will go to Avast or AVG plus Tiny. On this one I run Panda which combines AV and firewall.