Does free antivirus software work as well as the ones you pay for?

I have used AVG Anti Virus, Zone Alarm Firewall, Spy-bot Search and Destroy and Ad Aware both spyware killers for years. They are all free for personal use and I have had no trouble with Viruses Trojans Hackers etc. I have just upgraded to AVG free 8.0 and all seems good so far. Zone Alarm allows a lot of personal configuration unlike the Windows Firewall. They can all be downloaded from a href="http://www.download.com/" rel="nofollow"http://www.download.com//a I also use Windows Defender from the Microsoft site. It is safe to use two anti-spy products but never use more than one A/V as it can cause conflicts. You should run A/V and anti spy weekly. Hope this helps