Please follow the below mentioned steps:
1 - Remove the power cable from CPU (Remove battery if Laptop)and press Power On button from CPU.
2 - Now reconnect the cable (Reinsert the batter if Laptop) then turn on your machine.
3 - Keep watch of the screen at the bottom you see Press F2 or F10 to goto setup. Press the repective key to get Setup Page.
4 - Now Restore the settings to factory default settings.
5- Save the settings and restart your machine. Now it should work fine now.