you can try several password which you use usually for your internet world.
If not matched then you may try to use a formatted USB flash drive where only the latest BIOS file will be there. Connect the USB on your system and try power off and power on. Your BIOS may detect the latest BIOS file on USB and may run the old BIOS.
If the above process will not work you may have to open your system only to disconnect your motherboard battery for few minutes and then rub that on a clean cloth and place that where it was. Definately your BIOS password will be gone.
Thanks in Advance