No, your computer doesn’t have a virus. At least not the one that flashing popup is making you worry about.
Real tech support companies generally don’t use the “Free Security Scan” advertisement. Instead, that’s probably a scammer trying to get access to your computer or financial information. Don’t click on those ads, and don’t call the numbers they display.
If you have brand name anti-virus software on your computer, call that company. Or take it into a local shop, which will probably have a business license and people that can answer your specific questions.
Unusually for this blog, this is unfortunately not a problem that we, as accountants, can assist you with.