I have a Toshiba Satelite L455-S5009 - While on facebook, the computer suddenly shut itself down and restarted. When it came back up, all I have is a black screen with a blinking curser. Tried shutting it down again and back up to the same result. Tried removing the power cord and the battery and then plugging in just the power cord and restarted and got the same result. What happened and how do I fix it?
Let me guess - While on Facebook, you clicked on a link ?
You most likely now have an infected system.
Try starting the computer in Safe Mode & running your AntiVirus scan, for starters. Safe Mode with networking will allow you to access internet, to download other scanners if need be.