I think the best Microsoft Security Essentials But Kaspersky very good Anti-Virus

I use Kaspersky.

I use AVG, works great

AVG

Kaspersky

I use NOD32 Smart Security 6. Some former versions were really bad, but they managed to improve and be competitive against other good internet security suites. I don't say it's the best but I never had a problem with it. It's easy to use and low on system rescources. By the way I don't give it a hard time by clicking on all kinds of untrustrful links. Then I would need a stronger alternative like Kaspersky.

Esetnod !!

Microsoft Security Essentials
free,updated,lite and microsoft

Avast

Kaspersky's the best.