You don't have to reformat. What is the name of the virus, I'll help you. Did you try Malwarebytes AntiMalware? What was the result?
You may be able to shut off the visible virus app with task manager, enough to get control of the machine. If not boot to safe mode. Somehow either you or your fixit man has to get mbam running. You could start with hijack this, just google the questionable entries before you delete anything. Don't use Hijack as uninstaller.