This is pretty much a duplicate of a post I did in Dec2013. In transferring it from my FB page to here, I clicked the link in it and found they'd done a fresh review and it was even worse.
If you've been running Microsoft Security Essentials as your antivirus, you should absolutely replace it. MS has so much as said they plan their AV to be a bare minimum and not much else. When it was new, it was testing very well but has been slipping consistently.
I used to be an advocate of free AVs but, after a plague of infections two years ago where most of the infected PCs were using free AVs, have been forced to reconsider.
As a result, I have found "Managed Antivirus" (MAV) which I can not only provide to users but help strengthen as well. When I clean up a PC and remove tons of toolbar/browser hijacks/etc, I save the scanner's log file and can add much of the files to MAV's blacklist. In this way, I can keep a lot of non-viral junk off of my customer's systems.
If you would like more protection on your system, contact Prompt Care.