Most people who respond will have a wide ranging opinions, so expect to see a lot of different answers.
Many people in the forum run Microsoft Security Essentials as their choice.
Malwarebytes is also popular.
You also have the option of going with the paid versions such as Norton. Which paid version of an AV is best, is also a matter of opinion.
False positives are, unfortunately, a part of life. They happen occasionally to any AV/Malware scanner and if you have any questions about a file, Google is your friend. Or the forum for the AV/Malware scanner that you are using might provide answers.
If you look at AV test results, don't be surprised if you find 10 different answers from 10 different tests.