open device manager.
To do so, click on start > right click on computer and select properties.
select Hardware and then select Device Manager.
There, u will see keyboard option, expand that and then right click on the option listed under it.
Then select uninstall.
Now restart the notebook to get the keyboard drivers reinstalled.
Now, if the issue persists, the updated BIOS installed for your notebook.
If still the issue persists, u need to replace the keyboard.