You need to get the password from whomever set it. Failing that, you will have to contact Sony support and you will probably have to provide proof of ownership and ship it in to Sony. That is the whole point of a BIOS password - to make it pointless for anyone to steal it as they won't be able to use it. If someone tries to sell you a machine with a BIOS password and they can't tell you the password, you need to contact the police to be sure it isn't stolen.