I got a second-hand Lenovo g40-30 laptop this week and it was good as new but yesterday as I was just browsing through internet then suddenly my desktop background just went white and froze. The screen was unresponsive for more or less an hour so I just shut it down with power button. But the next day I open it, login screen is invisible. I can't login. On top of that, it is so unbearably slow that I can't do the Shift+restart for me to troubleshoot. Is there a way I can "manually" reset it. I tried Shift+restart many times, it can't register input as it is very very very slow.