The previous edition of ZoneAlarm Pro took some blows from ZDNet readers, who complained that the software caused system instability and blue screens of death. We think that version 4.0, which sells for $49.95 (~£30), will entice these disgruntled customers back into the fold. This firewall-cum-security suite -- it features the firewall, plus a few privacy tools and a pop-up ad killer, but no anti-virus program -- now sports expert-style rules that let advanced users fine-tune Internet access privileges, an outbound mail monitor that watches for suspicious activity that could indicate a worm, and a way to report Web intruders. ZoneAlarm Pro remains so easy to use that even a novice can manage it. Not all is rosy, however, as there's still no way to call the ZoneAlarm help desk. If you're already using ZoneAlarm Pro, upgrade only if you want access to the expert rules. Looking for your first firewall? ZoneAlarm does the trick, but only if you already have anti-virus software installed.