I heard from a friend to try out Malwarebytes to scan for viruses. It's free and it works really well. I reviewed it first since he said that there are lots of fake antiviruses. It only takes about 10 minutes to scan my computer and it finds stuff that some of the others don't.
Here's an article with some good info and links to free and useful software.
http://www.e-geniuses.com/news/2008/...apps-you-need/
Keep in mind that things change often. Software that worked well yesterday might not be effective today. I would recommend making friends with some techie people.