I'm going to cut through the bullshit before even finishing reading this thread (I have done this too often over the past 15 years).
NEVER BELIEVE SOMEONE WHO SAYS THEIR CHOICE OF AV IS BEST !But first I am going to recommend Avira as the best free AV solution.
Next I want you too ask me to prove it.
So I will.
Avira is consistently in the top of the charts, and is currently number 2.
AVG and Avast are pretty level, but not so hot on Pro-active protection.
Avast is doing OK, but dropped down the chart a little.
Micro$oft seem to be screwing things up, as they have dropped way beyond what I expected.
Virus Bulletin : VB100 award - latest comparative
Virus Bulletin : VB100 results summary
Comparatives||tests - reviews - reports
WARNING
Never assume that because your AV has not screamed at you, that you do not have some malware.
Most users of average-ware (such as Norton and McAfee) have usually got malware, and at some point been warned about loads of harmless cookies and false-negatives.
Use a first line of defence between you and your AV (there are even FB plugins).
VISIT NOW->Doc Flay-Anti-Malware
Use a more secure browser like Opera and Firefox (for the paranoid or just naughty, Opera has certain advantages)
If you use Java, make sure you set it to delete temp files, check for updates every day, and enable the security options that are stupidly switched off.
Block known harmful sites with a hosts list Blocking Unwanted Connections with a Hosts File