NO! DO NOT USE ZONE ALARM!
It used to be a good program but starting with 6.0.667 something went terribly wrong. View reviews at download.com and on the Zone Alarm sites Forums page, where hundreds of mad users are begging for help. I complained and ZA ERASED my comments!

I loaded the most recent upgrade and ended up with my business closed for over a week, and $1,000 in tech service bills.

Zone Alarm, what a pain
This damned programme infiltrates your system, creates endless log files and is a total bitch to get rid of. It sticks in msconfig and can you hell as like uncheck the box, even when you have supposedly uninstalled it. It is there, lurking, causing endless conflicts. Use Sygate personal firewall, it works. Be ashamed Zone Labs, fax you, pay you premium rates for a techy with my VISA, the hell I will. Just tell the general folks how to delete the thing.

Zone Alarm = HEADACHE, AGGRAVATION AND WASTED TIME AND $$$!!
Downloading and installing zone alarm was THE WORST mistake I've made since owning my computer!

Immediately upon attempting to install this product my computer shut, restarted, then shut down again. My computer repeatedly continued to do so until I paid a skilled tech to come over and attempt to fix the problem. He was able to get my computer operating again but my access to the internet via cable modem timed out after about 8 minutes. The only way to re-access the internet was to completely reboot, but my internet access still continued to time out after 8 minutes. My internet provider believed the problem was not with my internet access, but with my computer. After uninstalling this zone alarm piece of junk and uninstalling my other anti-virus software, the issue was still not resolved.

In the end I had to do a complete system restore on my computer. Right now I have, (12 hours and $100+ dollars later),
finally gotten my computer back to normal (almost).

Based on previous reviews and my techs analysis, there was a conflict with Zone Alarm and my already installed anti-virus software that was not resolved by uninstalling Zone Alarm. Apparently "uninstall" doesn't mean "COMPLETELY uninstall" Zone Alarm.

This product is worse than any virus I've ever encountered. If you decide to install it after these reviews, then caveat emptor (even if it is free) and heaven help you!

latest version is a bomb
I used to love zone alarm. I first used the free version, then upgraded to ZA Plus. Program worked beautifully, no problems at all. Then came the notice that ZAPlus was being discontinued, and the company was providing a free upgrade to the latest version of ZA Pro. Like an idiot, I downloaded it, and have nothing but problems since doing so: very slow boot-up and shut-down, system hangs and crashes --ZA Pro even temporarily disabled my AV e-mail scan. Some advice for prospective zone alarm customers: DO NOT USE THE LATEST VERSION OF THIS PROGRAM (v.5) It is filled with bugs, and ZA tech support is not being of much help. (They advise you to uninstall and go back to a previous version, or disable various other programs to see if there's a compatibility issue. Don't know about you, but I have better things to do with my leisure time)

It's really a shame. ZA used to be one of the best firewalls around.

It is a piece of rubbish, Do NOT buy.
ZoneAlarm has gone from being one of the best Windows Firewalls on the market to quite possibly the worst. If you are lucky it will serve you well. If you are unlucky you will find it buggy, and want to uninstall it ; that's when your life will become miserable. The uninstall procedure is completely broken. Zone Labs document an extremely complicated way of uninstalling it manually, involving deleting dozens of system files manually and editing the registry. This procedure is not something the average user will want to contemplate doing. Even after following this procedure many people, including highly qualified and vastly experienced computer professionals, are left with partially or wholly crippled PCs, their only recourse being to wipe the hard drive and reinstall Windows and all of their software from scratch. Do NOT buy Zone Alarm, it is utter garbage. A much better idea is to buy a hardware based firewall/router.