I was having problems with my new computer (HP Envy m6, running windows 8). It was not signing me out properly and would not shut down. I thought that maybe I just needed to update the windows software. But upon updating the software and turning my computer back on it gave me a black screen with one blue box that says "Selected boot image did not authenticate. Press <Enter> to Continue. If I press Enter the computer the computer turns off (turning back on displays the same message). If left on nothing changes and it will continue to run the computer.
Please help me, thanks :