Maximum PC has an excellent article online today highlighting 4 major steps that every computer user needs to use in order to keep their computer free from malware like spyware, trojans, viruses, rootkits, keyloggers, and other destructive software. This guide also provides information that you can use to remove malware from your system - although to do so successfully may require more computer knowledge that the average person may have. (Improperly removing malware can cause as much, if not greater, damage than the malware to one's software installations.)
As a technologist, I see almost daily major cases of malware infestations that cost the user far more than the charges of an expert to cleanse their system. I've seen infestations that resulted in identity theft and the exposure towards tens of thousands of dollars of bogus charges as well as major problems for one's credit. In a majority of these cases, the user did have some basic system protections in place on their computers. However, the source of the cause of the infection was not a failure of the security software to detect the malware, but the carelessness of the user to fall for the social engineering tricks that malware developers use to trick people into voluntarily downloading the malware.
Read the article. Bookmark this article. Print this article and keep it handy. Be cautious and alert as you use your computer on the internet. If in doubt, DON'T.