You'll have to make that decision yourself but IMO it's potentially dangerous to access the Internet without a personal firewall unless you're behind an expertly maintained server firewall. I have my ZoneAlarm set to log 'hits'. Hits are attempted accesses to my PC other than those I've told Zone Alarm to explicitly allow. I've not analyzed my log, but a cursory examination of it yields about 5 hits per hour of online time. Zone Alarm has the ability to tell you where the hits originated and once in awhile I go look a few up. I've yet to find one originating from an owner I recognize. Frequently they're from an ISP's pool of IP addresses which to me means some individual logged on to that ISP is scanning IP's looking for a potential victim. I'm no Internet plumbing expert so I'm sure there are many other possible explanations for the source. Maybe Tim could and would enlighten me, too.

McAfee and Symantec (the Norton AntiVirus folks) update their software and/or virus signature files about once per week. I check every other day or so. It only takes a few moments to check and it’s worth it to me to avoid a virus or trojan or other undesirable electronic critter.