Hi Marianne,
While this may be a hardware issue, it's always worth trying the following.
Shut down the notebook, 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 and see if this will launch the Start-up Menu. If it does, 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