Firstly, try this:
1. Pull out the battery and the power cable.
2. Press and hold the power button for about a minute.
3. Put again the battery and cable.
4. Press the power button to see if it's working.
Secondly, if that doesn't work, try to boot into Safe mode your PC? You could restore Windows by using an CD.
On third place when restarting your computer, press the appropriate F key to navigate to the Windows menu. From there you should have access to restore your OS. Open the Command Prompt in safe mode and run the command:
sfc / scannow
Then press Enter and wait for your OS to be repaired. If you cannot access this menu while you reboot, enter the BIOS settings. There, navigate to the storage to verify that your hard drive is as a first boot priority. If not, set it!