My lenovo laptop starts up but it shows a blue screen

Hello, My lenovo laptop shows a blue screen when I boot it up this started happening when I clicked update and shut down now when it starts up it just shows a blank blue screen I also had a virus on their when I shut it down so could that be the problem or did I accidentally unistall something important? please help this laptop was very expensive and we don't want to bring it in to best buy or some sevice center