ESET NOD32 Antivirus v3.o
I like this software because it could detect all viruses, trojans, worms, adware, spyware, etc. that might harm your computer. The scanning engine can also detect potentially harmful applications which some other softwares could not detect. This function is very important because newer threads were made to disguise as system files to avoid being detected. NOD32 also light and does not use a lot of system memory therefore would not slow down your system. The installer size is around 17MB only and will only took up to 30MB of your disk space.
NOD32 have the important Real-time scanning that will automatically scan removable drives and any files being accessed. Most of free antivirus software does not have this function or not good enough to detect the potentially harmful softwares. It also have the email scanning ability and really useful with Outlook. Another important feature is the web protection function which scan all the internet or network traffic.
The software is offered in both 32bit and 64bit version and updateable via internet. The software will automatically update the virus definition whenever there is internet connection. The antivirus can still offer maximum protection even if you don't update the virus definition due to its powerful protection ability. The only drawback is the software is only suitable for users with internet connection because there are no standalone or offline virus definition update. I believe almost all antivirus softwares do not offer any offline updater to avoid being exploit by software piracy.
BitDefender Antivirus 2008 & 2009
This software have very powerful virus scanner and offer users to manually set the scanning option. Standard settings have option for memory scanning, system disk, documents folders, and full system scan that will thoroughly scan your system. The scanning engine is so powerful that it can detect all harmful or possibly harmful applications. The software does not take a lot of disk space or memory and even old computer can run the software without problem. BitDefender also can protect your system without daily update because it can detect potentially hazardous applications. SoftWin offers offline updater until end off 2007. There is no more offline updater due to software piracy.
The Real-time scanning will scan any active application, links, or network traffic so for a slower computer, you'll notice the real-time scanning will slow down the system a little bit during the scan. The firewall feature is very powerful but sometime it does not automatically block or quarantine the harmful applications but ask the user for further actions. It is very important for users to understand any pop-up message because eventhough the software is very powerful, users might accidentally allow their system being attacked just because they don't really understand the message. The pop-up messages are also quite annoying because almost every action need further input by users. I don't recommend the use of BitDefender Free Edition 8 because it does not have the real-time scanning feature which is very important.
Used in the past:
Norton Antivirus 2002-2005
Used the software from 2002 to 2005 before the introduction of Brontok virus/trojan in 2005 that does damages to a lot of computers worldwide. Norton Antivirus offer good scanning capability but really slows down the system maybe because it took up a lot of memory. During the Brontok problem, even the latest virus definition update could not detect the virus. I've only able to cure my system by using BitDefender because it detect the virus as possibly harmful application. The only advantage at that time was because Norton offers offline definition updater because I don't have internet connection at home.
I don't like them:
Most of my friends use AVG Antivirus but I don't know why. I don't like it because it scanning ability really depends on it's virus definition update. If the definition was not updated for a week, your system can already vulnerable to attacks. Sometimes AVG cannot detect viruses that can be detected by more powerful softwares.
Don't like it because it makes my computer "hang" right after installation and only recovered by removing the software. Scanning capability is quite similar to AVG.