If it is a BIOS System Password, and the machine is out of warranty like my Inspiron 1300, Dell will SELL you the master password for about $50. Proof of ownership seems to have nothing to do with it. This is a total rip -off. Dell installed it, didn't tell me about it, and now wants me to pay for access to MY computer. I don't care how old it is. It's like a car dealer locking your keys in the trunk, and the charging you to get them out. I have several Dells on my network, and I don't think I will be replacing them with new Dell computers any time soon.
Proof of ownership is ESSENTIAL - they WILL NOT supply the password without it. If you are under warranty and the system is YOURS, there is NO CHARGE for the call. If you're out of warranty, as with ALL vendors these days, there IS a charge for the support call. If the system was purchased second-hand and you do not have a transfer of ownership in hand, you must get that before you call - the purpose of the password security is to ensure that only registered owners have access to the data on the system. It's not a perfect system by any means, but it DOES safeguard your hardware in case of theft or loss.