When I put a system together for someone, one of the first things I do on the Web after setting up the eMail account and connection settings is go to
www.pandasoftware.com or
www.grisoft.com and get an antivirus utility installed and set, then updated. Then I'll cruise to
www.sygate.com or
www.zonelabs.com and find a firewall. If the new owner has bought or specifies another antivirus or firewall package, I'll use that.
Then we make browser choices (IE with or without Maxthon/Avant, Opera, Firefox, Netscape).
Firewalls and antivirus are mandatory if you use IE (any version) and/or are on broadband (ISDN, DSL, videocable, satellite). Antivirus is mandatory and firewall is recommended if you use W3C browsers (Firefox, Opera) or Netscape on dialup.
Spyware scanners should be run periodically (AdAware, SpybotS&D) and can be set resident. Never set more than one of each (antivirus, antispyware, and software firewall) resident, the programs will contend and hog resources.