These links contain all you should ever need to keep your computer running smoothly.

I personally recommend the first three.

They do a fantastic job all by themselves. If you prefer not to manually update your programs, PLEASE use the paid versions of these three programs. I have used the free versions for nearly a decade on our personal computers, and have NEVER had to do anything more to keep our computers free of malware and spyware. I have however, been paid to clean many, many computers that used other security programs, that had become horribly infected with spyware, malware and viruses.