From what I understand BlackIce is really an intrusion detection program, ZoneAlarm is an actual software firewall. I have used both and now I only use ZA because it will block intrusion attempts, will control OUTBOUND internet traffic (which is helpful if you catch a trojan like BO), and besides being free, Zonelabs provides free updates and bug fixes. BlackIce does not monitor outbound internet traffic, and costs $39.99 for a ONE YEAR license. Bug fixes and updates are no extra cost during that one year license. When that year is up, you will have to buy in again for further updates and bug fixes (BlackIce needed major bug fixes for Win 2k and Win ME which is basically everytime MS updates their OS's, BID needs some sort of fix due to undocumented dll's, these bugs rendered BID unreliable until patched).