Best FREE Anti-virus program?

I have Windows Vista, I was using McAfee, but my subscription ran out and I don't have the money to buy it again. So Does anyone know the best antivirus software to use that is free? Prefereably one that works well but doesn't slow down my computer.

Best FREE Anti-virus program?spyware removal

AVG free edition is the best and it's Vista compatible.

[EDIT] William V is basing his opinion on a 2 year old research done by the link provided in his post. The new AVG 8 is much better and even in the research it received low marks because of it's 'clunky' interface not because it is not a good FREE anti-virus program. I have been using it on my network for the past 4 years and never had a virus.

Best FREE Anti-virus program?virus protection software

try the McAfee 8.5 its the best
Hello,

The best Anti-Virus for free is AVG Free Edition.

Avoid avast! which is bad !

Comparative :

AVG Virus detecting rate : 90%

Avast! Virus detecting rate : 25%
There are many free Anti-Viruses out there, just some aren't as good as others, though saying that I wouldn't recommend using two.

AVG - http://free.grisoft.com/filedir/inst/avg...

BitDefender* - http://www.bitdefender.co.uk/site/Downlo...