Sounds like a scam. Happened to me before. After researching how to get rid of the garbage it became clear that to truly be sure it is gone a hard drive reformat is required. Not fun. You can try windows defender, spybot - search & destroy and malwarebytes. I have heard good things about kapersky but haven't used it myself. You may want to update the antivirus program and then restart in safe mode without networking.