Everyday there are more viruses, spy ware and other malicious little programs released onto the Internet in an attempt to steal data from or advertise to innocent computer users. No one anti-virus or anti-spyware program can protect you from it all which is why computer technicians usually have to use several different utilities to clean up an infected system. One of the most comprehensive and easy to use utilities is Malwarebytes.
I like Malwarebytes because it is a free program that seems to catch more spyware and viruses than any other software available. Of course this is subject to change. It is likely that some other program will rank at the top in a few months as new malicious programs come out, but for now Malwarebytes is top dog.
To use Malwarebytes go to http://malwarebytes.org and click the blue Download button on the left. On the next screen, click the "Download Now" link and choose to run the program. Step through the installation. When it is completed, Malwarebytes will run. You can choose a quick scan and a full scan. The full scan can take 4 or 5 hours to run. Click on "Perform full scan" then click the "Scan" button. When the scan is completed you can click the "Show Results" button to see the infected objects. Here you can click "Remove Selected" to clean up the infections.
The free version of Malwarebytes allows you to scan on demand like this for no charge. If you would like to schedule automatic scans and have an always running shield, you can purchase the full version of Malwarebytes and http://malwarebytes.org for about $25.