Look to Frys.com for free commercial, (after rebates), antivirus or suites.
At one time or another you'll find Kaspersky, Norton, Trend Micro, Webroot and others for free after rebates.
After using Norton products since the time Peter Norton was writing his own software, I swore off them completely around 2003 or 2004. After the Symantec buyout they had become all but useless.
I tried McAffee,(awful and still is), Trend Micro, (very good then, not so much now), and Kaspersky, (good reliable antivirus), then settled on Nod32 from Eset which was light on resources, fast and wicked effective. However, Nod32 HAS become more bloated over the years AND more expensive.
I used Microsoft Security Essentials and then Microsoft Security Essentials 2 beta, (google it), over a period of about 8 months on my desktop and my wife's laptop. That in conjunction with Malwarebytes, (free), is a very effective and light combination.
Recently I decided to give Norton another look due to the very high marks it was getting in reviews online. I picked up a copy of Norton Internet Security from Frys.com for free after rebate and installed it first on one of my XP Virtual Machines. After about a week of trial I went ahead and installed it on my desktop and my wife's laptop. I find it relatively light on resources, does not hinder web browsing, doesn't slow down boot process any more than any other antivirus and, I think, worthy of anyone's consideration. I've not had time to judge it's effectiveness but if you do a couple of searches you'll find plenty of reviews for that.
One thing I need to mention is the firewall in the security suites. I've stayed away from them over the years because I just hated the almost constant popups asking whether I wanted to allow this or that process access to the internet etc while it was in it's learning curve. Well, that appears to be gone. They've instituted a "smart firewall" that calls on the experience of the Norton installed user base to determine if a process is legit and if so to allow it access. It will take a bit of tweaking to get it to your likes but overall I have to give a thumbs up to Norton, either the antivirus or the suite.
I used Kaspersky Antvirus for about a year and was quite happy with it and would still recommend it, especially if you can get a deal on it.
A couple of things to bear in mind. Windows Vista and Windows 7 come with a 2 way firewall and Microsoft Windows Defender. Ok, their effectiveness can be argued but they are there and can be tailored somewhat to one's needs. Windows XP or before only provides inbound protection but Microsoft Windows Defender can be installed for free.
Also, my wife and I are in our 60's now, (jeez, how'd that happen?), so no children to worry about online and our web surfing habits might be different than others, so our security needs might be different than others.
So, if you want a recommendation from personal experience for an antivirus/security suite on the commercial side, I would say the following, in no particular order, are worthy of consideration and some can be had for free;
Nod32
Norton
Kaspersky
As to the choices in the free realm, I only have experience with Microsoft Security Essentials and Malwarebytes Antimalware. Both, in my opinion are excellent products, and together make a very effective defense for your pc.
Hope this helps,
Larry
