I use sbc/yahoo as an isp. They advertize that they have antivirus. Do I need additional antivirus s

You need one antivirus program and one firewall installed on your computer.

Anti-adware/malware/spyware are ok to have more of.

Firewall Protection.

ZoneAlarm Firewall Free.

http://www.zonealarm.com/store/content/c...

Easy-to-use firewall blocks hackers and other unknown threats.

* Systematically identifies hackers and blocks access attempts.

Automatically makes your computer invisible to anyone on the Internet.

Use ZoneAlarm if you normally use Windows Firewall.

Disable Windows Firewall after downloading ZoneAlarm if it's not done automatically.

Ad-Aware 2007 Free.

http://www.lavasoftusa.com/products/ad_a...

Ad-Aware 2007 Free remains the most popular anti-spyware product for computer users around the world, with nearly one million downloads every week. Our free anti-spyware version provides you with advanced protection against spyware that secretly attaches and takes control of your computer, resulting in aggressive advertising pop-ups, sluggish computer activity, even identity theft through stolen bank details, passwords, and credit card account numbers. If you want real-time scanning capabilities, consider upgrading to Ad-Aware 2007 Plus for real-time protection against spyware, all the time.

SUPERAntiSpyware Free.

http://www.superantispyware.com/

AVG Anti-spyware Free.

http://free.grisoft.com/doc/20/lng/us/tp...

Spybot - Search %26 Destroy detects and removes spyware, a relatively new kind of threat not yet covered by common anti-virus applications. spyware silently tracks your surfing behaviour to create a marketing profile for you that is transmitted without your knowledge to the compilers and sold to advertising companies. If you see new toolbars in your Internet Explorer that you haven't intentionally installed, if your browser crashes inexplicably, or if your home page has been "hijacked" (or changed without your knowledge), your computer is most probably infected with spyware. Even if you don't see the symptoms, your computer may be infected, because more and more spyware is emerging. Spybot-S%26D is free, so there's no harm giving it a try to see if something has invaded your computer.