Any time you get an offer to a "free" virus search for your computer that you did not solicit, it is coming from the same company that put it there, and money you pay to have them remove it will be wasted.
Take careful note of the name of the company and google it, and that will lead to an antivirus program that will work.
Avira, AVG and Malwarebytes are all reputable and available for free, if you CAREFULLY read the directions for the free version. Their ads are deceptive.