My laptop is in restarting mood for over an hour!

Hello,

i have vaio sony laptop everything was fine until today. I almost never shut down the computer. So today when I traied to login, I couldn't use the keyboard as it wasn't typing anything, so I used the screen keyboard to login and then I chose to restart the computer. And since that the computer is restarting. O tried to shut it down manualy but couldn't. Plz help!