Windows Security Essentials

Many people are paying hundreds of dollars for anti-virus and anti-malware software on their computer.  After the initial investment, some companies offer to "keep your computer secure" for an annual or monthly fee.  These programs often bog down the system and cause annoying messages to frighten you into buying more of their products.  
This is really not necessary.  I have found for my personal use that Microsoft provides all that I need fro free.   Yes, Microsoft provides things for free.  
If you are running Windows XP or later (and most people are), simply goto http://windows.microsoft.com/en-US/windows/products/security-essentials and download the version for your system.    Take notice if you have a 32-bit or 64-bit version of windows.  You can tell this by right clicking on "My computer" and selecting "Properties".   You will see either 32-bit or 64-bit operating system listed.
After installation, the software will keep itself up to date and will actively scan files that you open.