If you have Windows 10, my computer man (the one who comes to sort out problems) tells me that Windows own antivirus is so good nowadays that you don't need to buy one. I've had my laptop for over 3 years now and never bought any antivirus software. Windows does its own virus check, daily, or weekly depending how you've set up the PC and each time tells me it hasn't found any problems, apart from once when it dealt with whatever the problem was.