Now here is the best, free and simple, security combination;

Download three FREE programs:

Your AntiVirus (which should be one of these):
-Avast! Home Edition

-AVG Free Antivirus

-Avira Free

-Microsoft Security Essentials

With a special Scanner:
-Malwarebytes' Anti-malware
-SuperAntiSpyware (Optional)

There are three free security programs that work incredibly well together.
Those AntiViruses are the best ones found on the market.

Malwarebytes': A malware remover, scans your computer and removes malware.

SuperAntiSpyware: An anti-spyware that does not only detect spyware, but also trojans, worms, tracking cookies, adware and a lot more.

Of course, if you have s slow computer, you do not need to have this program. AntiVirus and Malwarebytes' Anti-Malware are enough.

As long as you update malwarebytes and your AntiVirus program (and superantispyware) frequently enough, You are secured.