i have been asked over and over what antivirus/antispyware programs to use. Below are some of the antivirus/antispyware that are most popular and highly recommended:

Antivirus: 
AVG Antivirus Free Edition
AntiVir Personal Edition
Avast Free Edition

Firewalls: 

Comodo Firewall Pro

 Please note that Windows XP and Windows Vista both already contain firewalls. Using a 3rd party firewall those versions of Windows is not needed unless you feel you need more control over settings.

Adware/Spyware(Malware) Scanners: (You can use them all if you wish)
AVG Antispyware
SUPERAntispyware
Ad-Aware 2007
Spybot Search and Destroy

Other(proactive defense that requires no system resouces)
Spyware Blaster
IE-SPYAD