As Ethel has indicated, most of the 'regulars', here on AB's technology section use Zone Alarm Free Edition for their firewall, together with AVG Free Edition as their anti-virus program.
Most people seem to use Ad-Aware SE Personal or SpyBot Search & Destroy for anti-spyware protection, although AVG's new anti-spyware program is also gaining in popularity.
You shouldn't install any new anti-virus or firewall program until you've uninstalled Norton. You can't do this from within Add/Remove Programs and it doesn't have its own uninstall option. You need to use the uninstall tool, which is available here:
http://service1.symantec.com/SUPPORT/tsgeninfo .nsf/docid/2005033108162039
Chris