(edit: sorry I think the version I used was 2.1.5, been a long time ago) I used to use Kerio PFW when running XP. Now running Win7 and have been unable to find a firewall that has the real time logging feature of the old Kerio PFW. The things I miss most are being able to see connectiong real time, data being transferred, whether inbound or outbound, protocol being used, rule being applied. The other thing I miss is the simple alert as to whether or not to allow a program. You could get a real good idea of what is happening to your PC in real time and even if you're not a networking wiz you could figure out any problems simply by watching the real time log. All of the free firewalls I have tried, and I have not tried them all do not allow this user-connection interplay. They mostly do things behind the scenes and you have to guess what they are doing real time. Doesn't really teach you anything, nor show you what is actually happening. Of the many, many free firewalls out there (or even paid if need be) there must be one that has this feature. Also when is some smart guy going to rebuild Kerio 2.1.15 so it works on Win7 and up? That company (cannot recall the name off hand) that supposedly took over Kerio is no good. I tried their so called revised kerio firewall and it blue screened consistently. Anyone?
http://www.sphinx-soft.com/Vista/ The closest thing IMO is Sphinx. Works on 10 and 7 as well. Read the link for features. It's a bit quirky to use their alerts but it's the same idea as in Kerio, but it works fine with the predefined zones or you cook your own. Their forum is good, and the betas are very stable. Current is 8.0.2.38. I use the plus version. I wish we could have Kerio, I loved it so.
Sunbelt bought Kerio and issued Sunbelt firewall with few useful changes such as IP groups, web filtering and behavior monitor. The latest version 4.7.5 works only on XP-SP3. Good firewall.
Agnitum always, far as I know, wrote and owned its own Outpost. Then they sold or were taken over by yandex a year ago, maybe two. So it's abandonware. Outpost v9.2 and 9.3 still run fine on windows 7 (lifetime license here). Some people had problems with Outpost on 10, I think M$ was complaining. Don't know how their a bit outdated anti-leak, hips, works these days, but packet filtering and system monitors seem to work fine.
The outpost firewall technology has been incorporated into many other security programs,notably bullguard and avast.
I reverted to kerio 2.1.5 yesterday. For auld lang syne. On my XP computer in exactly 24 hours Kerio has used 1.437 seconds of CPU & occupies 376K of Ram. Kerio's main job is to monitor outgoing. My router's FW handles the incoming.