This happened to me i believe its a Windows issue. I repeatedly hit the f10 button before the vaio start up pic came up. Not sure why but it worked, BUT*** you have to do it immediately when you turn on the computer.
I think its been set back to factory settings. All my stuff on it has been deleted but im currently doing a vaio care rescue. Fingers crossed all my stuff is still on it when its done. Good luck hope this works for you!!
Bre