I had been Zonealarm using for the past 6 years. Before that was Norton Internet Security (which is a memory hog, and does not perform well at all).

Initially, the earlier version ZoneAlarm was good. Strong firewall and easier to configure. But since beginning of this year, the newer version is a memory resource hog. Eating up my resource, slowing down my PC. Worst of all, it interfere with my p2p, causing the PC to freeze. The culprit was the TrueVector. Did some research in ZA forum, and found out I'm not alone. The solutions offered by forumers in ZA forum, like clearing the Internet Log, temp files, RDB files, ldb files, etc. weren't helpful at all. So, I stop using ZA.

My favourite choice are:

1. Outpost Pro Firewall v4.0.1007 which is what I'm using now. I think it is a very good firewall. Strong and secure. Difficult to kill. Slightly troublesome to set up. Initially there was a lot of message pop-ups asking you what to do with any apps. After a week of usage, it became lesser and lesser (it's learning). And it does not interfere with my p2p. Also not as resource-hog as ZoneAlarm.

2. Comodo Firewall is another good one. It is secure and non-leakable. And it's FREE! I tried this, but then decided to go for the Outpost. Reason being, the Comodo blocks my ActiveSync's port. I set the rules for it, but unable to open up my ActiveSync port. That's the reason I use Outpost firewall till now.