Grwd, SJP,
I finally dumped Norton after some of the same problems as grwd reports. I went to Avast! because it integrates very well. There is a free version for non-commercial use. Updates are smooth, and you can choose what it scans and how often. I especially like the email scanner.
SJP, as to whether or not we really need an AV program or firewall, I went for years without. I never got a virus, but felt vulnerable, when I learned how malicious code can be embedded in the ID3-v2 tags that are on some mp3 music files. Some kind of firewall is needed for broadband, and many recommend Zone Alarm. I also recommend some sort of spyware protection, such as AdAware or SpyBot, since I was troubled by spyware, even if my computer remained virus-free. I use ie-SpyAd to automatically put suspicious sites in my Restricted Zone.
Norton tends to take a "brute force" approach, and, if you have their Internet Security Suite, will even break the javascript on a page. Plus, Norton 2005 slows down my tired old machine so much as to be unusable (Norton stopped supporting subscription-based virus def. files for Norton 5, which ran smoothly on my machine, as of the end of last year).
Prior to Norton, I used McAfee, although I switched to Norton on someone's advice, because it was said to be more in tune with a Windows OS.
All the above was put in place before I switched from IE to Opera, which I love. Opera 8.02 incorporates all the best features of the latest IE, Netscape, and Firefox, plus, it runs much faster on my old machine than any of those. I had used Netscape prior to IE, but wanted to try going all Microsoft, to see if the integration made any sense. I use the Windows Updates judiciously, and have dreams of someday going Linux or switching to a Mac.
My 2-cents worth has turned into a long post, but I had this urge to vent.
Howard