Take the battery out when PC is shut down and turn OFF the power switch on the back of PSU and when the battery is out, start the PC and it will reset BIOS to default setting.
Put the battery back >>> switch power ON on the PSU >>> Start button.
iirc in bios, leaving your new password field blank after you enter the current password deletes the current password.
unless you actually changed your password to the word 'blank'.