Here are some troubleshooting steps that you can try that may help.
- Start by doing a hard reboot, remove its battery (if not built in) and unplug its AC adapter then press and hold the power button the boot it back up then try it again.
- Next is to uninstall/reinstall the keyboard driver from Device Manager.
- Once you've uninstalled the driver reboot your laptop and it should reinstall the driver automatically.
- If these doesn't work run System Restore, put it back to an earlier date or time before the problem even happened.
- If System Restore will not solve the problem try and connect an external USB keyboard as well.
- Lastly if all these will not work you may need to reinstall Windows.
- And if reinstalling Windows will not work do check the ribbon cable that connects the keyboard to the motherboard because if that will not solve the problem last resort would be to replace the keyboard itself.