There are some good free Anti-Virus programs around - I use is AVG-free & Zone Alarm is my firewall.
http://free.grisoft.com/doc/5390/us/frt/0 - AVG Free
http://www.download.com/3000-2092-10039884.html - Zone Alarm
If you look at
Viruses/Pop-ups/Firewalls/Security -
Protect Yourself!!! in this Forum you will see more listed.
You should also have Spyware, Malware & Trojan Protection - Free ones are listed there.
Isisrose