Finding a great, free anti–virus program for Windows has been a challenge in the past, especially for a new version of Windows.  This time however, Google and PC Tools have come to our rescue with 'Spyware Doctor with Anti-Virus', bundled as part of the new Google Pack. Google Pack is a bundle of popular, free apps provided by Google and its partners. It includes Adobe Acrobat, Firefox, Spyware Doctor with Anti-Virus, Picasa and several other apps.   If you are just looking to protect your new home PC or laptop from viruses, then you’ll probably just want to download Firefox and Spyware Doctor with Anti-Virus. These two apps together with the new and improved security built into Windows 7 will go a long way to help keep your PC safe on the net.
 
In our testing, we’ve found that Spyware Doctor with Anti-Virus does a good job of protecting your PC from new viruses. However, if your PC is already infected with a virus, then you’ll probably want to pay for the full version which offers more powerful removal tools. Aside from the fact it’s free, Spyware Doctor with Anti-Virus has also recently received the prestigious PC Magazine Editors Choice award.

So this is our top pick for the Best Free Anti Virus Program currently available: http://pack.google.com/ 

Note: Don't have Windows 7? The Google Pack also supports Windows XP and Vista.