What is a good AntiVirus program that I could download for free?

The best protection for your computer is a 3-tiered approach:

[1] anti-spyware software

[2] anti-virus software

[3] firewall

[1] Latest list of Firewalls (use only one at at time)

http://securitynewsfromthenet.blogspot.c...

[2] Latest list of Anti Virus programs (use only one at at time)

http://securitynewsfromthenet.blogspot.c...

[3] Latest list of Anti Spyware removal tools

http://securitynewsfromthenet.blogspot.c...

http://andymanchesta.com/

What Does AntiSpyware Do?

Antispyware helps protect your computer against pop-ups, slow performance, and security threats caused by spyware and other unwanted software. To keep up with the latest forms of spyware, you must keep your antispyware updated.

http://www.microsoft.com/protect/compute...

What is antivirus software?

Software that scans your computer's hard drive for all known traces of viruses. After the scanning is complete you can usually choose which viruses to delete.

http://www.microsoft.com/protect/compute...

what is a firewall ?How does it work?

Is a security program which protects your computer from unauthorised access through the Internet. It resides on your pc and filters traffic coming and going from your computer

http://computer.howstuffworks.com/comput...

http://www.microsoft.com/protect/compute...

Windows Personal Firewall Analysis

http://www.matousec.com/projects/firewal...