I have a short version and a more detailed version, for those that want more information about a particular product look just after this first part.
But first the Short Version:
Norton Antivirus: Works but is Big and Resource intensive Bloat ware.
McAfee: Works, less resource intensive than Norton Antivirus, but they made downgrading almost impossible so I decided to move on.
CA: Computer Associates was the next attempt but this was system resource intensive. They were also a bit more expensive than other options.
Zone Alarm: This one was so User Intensive with pop-up's letting me know some program started, was wanting start or access the network or save a file I had to remove it quickly.
AVG: I tried the free version and liked it so much I got the paid version. Things were going well until I noticed my network speed was slowed by about 70%. Long story short AVG was checking every packet entering and leaving my computer. This was one of the features on the paid version so I went back to the free version for a while.
Avast: Good Free product. I used it until MSSE.
Microsoft Security Essentials: Great Product, low system resource load, almost no user work load. It has already caught a virus (mp3) on a friends thumb drive. This is what I use on all 4 windows machines in my house today. (and my mothers)
I have been using antivirus programs since about 1998. At this time these were DOS based programs and worked in the background, or Terminate and Stay Resident (TSR) as they were known in the single tasking DOS OS. I was a big fan of Norton Utilities since version 1.0 through 3.5. Somewhere in this time frame Symantec bought Norton Utilities and produced an AntiVirus program under the trusted Norton Utilities name. This is when I decided to give it a try, as Viruses were starting to be a real problem. I purchased and used Norton Antivirus (NAV) as they called it for many years. I continuously used these utilities to keep my system operating as speedy and efficiently as possible, but I kept noticing my system slowing down. Norton Utilities & NAV continued to grow in size and complexity. I longed for the small simple utilities I had learned to love, but it was not to be. In 2001 I upgraded to Windows XP when it came out. It started out ince and speedy, from what I was use to but by the time I installed all my software it was running just a slow again. I was not happy. One weekend I was determined to find out why my system was running so slow. I started to remove all the TSR programs. I still called them that even though by then Windows XP was somewhat of a multitasking OS. NAV was the last one of those to be uninstalled, but on reboot the task manager reported NAV still running. In other words NAV failed to uninstall. This is when I lost confidence in the Symantec line of software. They couldn't even uninstall it properly, so why should I believe they were doing a good job of writing it in the first place. I never purchased another copy of Symantec, Norton AntiVirus.
By now it was around 2002 and I was familiar with McAfee Anti Virus and decided to give them a try. I tried the free version first, liked the lower resource load on the computer. It was running much better. I upgraded to the paid version and was happy with McAfee for a year or so. I couldn't see any difference between the free version and the paid except the AV engine always seemed to be on or two versions behind the paid version. It came time to renew, I tried to go back to the free version they were offering but they put up so many road blocks I decided to move on.
Computer Associates offered a free version, I tried it for a while, but they too made it very difficult to stay with that version. A lot of nag screens did it for me.
Zone Alarm was my next product. I started with the free version and stayed with them for about a couple of years. At first I liked the popup asking if a program could access the internet, and it remembered the setting. The pop-ups keep coming, most of the time with insufficient information to know who was asking and for why. I realized that this was not security if I was blindly clicking ok every time I wanted to go to the internet. There had to be something better.
AVG had a long history of good quality Antivirus programs so I decided to try this next. When I installed the free version of this program, it worked so well that I was concerned if it was doing anything at all. Then comes a day when it flags a download as potential virus, quarantines it and I deleted it. By now it was 2007 and Verizon FIOS comes to the neighborhood so of course I sign up and get great Fiber speeds, 15meg down, 5 meg up, to the house. The speeds were as advertised and life was good. In 2008 I volunteered to rip some audio CD's, Class lectures, for my church and upload them to a their website. I couldn't get more that 200k/sec up. ???? I called the website and they had no problem on their end. I called Verizon and complained they sent me to their speed test at verizon.net/micro/speedtest/java/ . That reported the correct speeds. Not that I didn't trust them I went to www.speedtest.net tried again and got the specified 5 meg up speed so the problem couldn't be on my end, or could it? I decided to try another machine, one I was working on and had just done a clean install. The upload went at the proper 5 meg up…. How could that be? Could this be Anti Virus? None was installed on the machine I had just used. I started by disabling AVG on my primary machine and the speed bottle neck went away. I looked into it a bit deeper and found the problem was in a "feature" that only came with the paid version, so I immediately downgraded to the free version and the problem went away. But this bothered me to the point that I started looking for another Anti Virus program.
Avast was highly rated and free, so I installed it. I had no speed problems. The processor overhead was small, the network overhead or slow down was not noticeable so this worked well for me. That was about a year ago. Starting a year after that install I started getting nag screens to upgrade to the paid version. This got old real fast. The good news is Microsoft had just released an Anti Virus add on.
Microsoft Security Essentials. (MSSE) I installed this on my system and was impressed with the ultra low resource load on the system and so far NO user required intervention. But the old question of was it really working started to nag me. Then came proof. The 13 year old son of a friend of mine managed to render his laptop unbootable. So being the tech geek I was asked to see if I could "fix it". I was able to get all the data, and music copied to an external drive, and I reinstalled the "Vista" OS, MSSE and all his software. When I copied all the data and music back to the newly rebuilt system I noticed the copy going rather slowly. Then I found out why, MSSE was checking each file as it was being copied back to the new system. Up popped a warning advising that one of the music files had a virus and the file could not be repaired. I deleted the file. To this day the laptop is working fine and MSSE is doing its job. I am sold on this simple invisible little gem. I recommend it to all.