Microsoft Security Essentials is a good basic antivirus program. It is clean and small and since it is free and from Microsoft it isn’t bloated with features many people don’t need. Norton and McAfee and their counterparts need to "offer more" to get you to pay $50-a-year for software that you can get for free from Microsoft.
If your computer is running slowly and having a variety of odd errors and lock-ups the best way to spend your money is on an anti-Malware program not PC Matic
Microsoft Security Essentials and Spybot Search and Destroy. Very good in their time I now am a big fan of Malwarebytes. It is a program that has both a free and pay version. The free version can help you once you are already infected The pay version will help you from getting infected.
Cleaning that type of infection off the system is one of the best ways to speed up your computer and fix many of those random errors and lock-ups.
So my advice, install Malwarebytes and run it at least once per week. ..... Jack
