For years, I've used multiple browsers as tools to help test newly developed web pages, so that they are compatible for any browser.  During the past year, I've settled on 3 choices (IE 6, Mozilla Firefox, and Opera 7.53).  

I like all 3 browsers and Microsoft has improved security extensively in the new IE that's part of XP SP2.  Firefox is one of the most secure browsers and today, Mozilla released their FireFox 1.0 Preview Release version.  In early testing, this is working well so far.   You can download the EXE version of Firefox 1.0PR from Mozilla's home page

http://www.mozilla.org/

FTP site for EXE and ZIP builds (includes MAC and LINUX links)
http://ftp.mozilla.org/pub/mozilla.org/firefox/releases/0.10/

Article promoting Mozilla FF to help combat spyware:
http://www.usatoday.com/tech/news/computersecurity/2004-09-08-zombieinfect_x.htm