There are many very good free antivirus trial software programs that outperform most of the popular commercial products. Many commercial products perform too many unnecessary scans that rob system resources and slow down your computer. There are several free high quality antivirus programs available for personal use. Avira, Avast, and AVG are the three top antivirus software programs that also offer a free personal use version. I have successfully used AVG for years and only recently changed to Avira because the better reviews. The 3 programs mentioned above are all very good and I would be confident using any one of them.
However, I do not use antivirus programs to clean infections from my computers. I have found that once you are infected that often other malware software is downloaded, such as, keyloggers, downloaders, spyware, and other malicious software that is sometimes not detected. When you think you have cleaned your system and log back onto the Internet you find yourself infected again. To prevent this I restore my operating system back to a known good configuration using imaging software. The 2 products that I have used often are Norton Ghost and Partimage. I like Norton Ghost because you can run it from DOS. Using DOS makes for a very quick recovery usually less than 10 minutes. I have also used Partimage which is a free Open Source clone of Norton Ghost. Another image program that appears very promising is Clonezilla. I like Clonezilla for it’s speed and ability to cast over a network.
I maintained hundreds of computers in labs and at various sites using imaging software. By being a little proactive in your maintenance you can avoid costly downtime. I even create hidden partition on client computers for quick recovery. I know from experience that clients will get themselves in trouble again and being able to perform a quick recovery is very impressive.
I have been teaching computer repair and maintenance concepts for over 10 years and have created some popular training videos on YouTube that can be found by searching the title A+ Computer Repair Training.