I'd erase the CMOS memory by removing the battery on the motherboard for at least ten minutes. Remove mains supply first.
If that doesn't work then you will have to use the jumper on the motherboard to clear the CMOS. Can you get into the laptop case? Do laptop motherboards have jumpers even....??? I'm not sure....
Instead it could be a dip switch in the memory hatch underneath the laptop.
Beware of ESD though
