Does Free Antivirus Software Work As Well As The Ones You Pay For?

I used to have Norton Antivirus, but my subscription expired. Is it worth it to pay to renew my subscription, or should I just download a freeware antivirus program?
What are some good free antivirus software? I keep hearing about Avast and AVG?

What Is The Best Free Anti-spyware And Virus Protection On The Internet?

I want to download a virus protection program on my windows vista laptop. Anyone have any good sucess with one type of anti-virus program that they would like to recomend? This would be much appreciated. I am currently running Microsofts Windows Defender, but want added virus and spyware protection.
Thanks…
Cory