If there's a BIOS password preventing you form making changes, ask the person you bought it from what the password is. If you bought it from Dell, go to http/www.dell.com, input the Service Tag reference found on the case and prove ownership to their satisfaction and they will help you.
We don't provide password help here at Tom's in case we inadvertently help someone hack into another person's system. That's why proof of ownership will be needed at the Dell site.