Which anti-virus software do you use?

Okay, i'm gonna Google it, look for more information, and read reviews to see what other people are thinking about it.
I also wanna thank you for the advice and i have just one more question: is the Free Avira as effective as the paid one?

I am Using Microsoft Windows Essentials as well and no problem at all. Before, I tried Norton 360 and Avast and they worked all good. As of now, I enjoyed MWE as it free and have a constant updates as well.

Guard is as effective as the paid version, however it lacks a firewall, mail guard (I don't use it and I don't think it's necessary) and web guard (useful, but not necessary if you have guard). For an average user free avira is just what they need.

Okay that's what i needed to hear, that the Free version is as effective as the paid one with the exclusion of the firewall, mail guard and web guard which i can have from another program.
So i'll just give it a try cause there is nothing to lose and see myself its performance.

I use Avast antivirus - Freeware edition along with Comodo Firewall - Freeware edition

Works great for me even though its free!

I've tried several over the years. Recently, I started using Avast and feel comfortable with its performance so far. I haven't gotten infected and I'm loving it. For a short time, I used McAfee and got infected twice. I definitely wasn't happy with having to completely wipe my computer each time because of it.

I use the AVG Free to catch most of the viruses. I also use the free (donation-based) SpyBot Search & Destroy. I also had or probably still have Resident Blacklist on here. I'm not sure if I updated it though. I have the best free services of this nature though, I know that (in my opinion of course).