Hi,
While this could be a hardware issue, it's always worth trying the following.
Open windows Control Panel, open Device Manager, expand Keyboards, right click 'Standard PS/2 Keyboard' and select Uninstall.
When complete, shut down the notebook - if you're running Windows 8 or 8.1, do this by holding down the left Shift key as you click on Shutdown to temporarily prevent a hybrid boot.
Then unplug the AC Adapter and then remove the battery. Hold down the Power button for 30 seconds. Re-insert the battery and plug in the AC Adapter.
Tap away at the esc key as you start the notebook to launch the Start-up Menu and then select f10 to enter the bios menu. Press f5 to load the defaults ( this is sometimes f9, but the menu at the bottom will show the correct key ), use the arrow keys to select 'Yes' and hit enter. Press f10 to save the setting and again use the arrow keys to select 'Yes' and hit enter.
Regards,
DP-K