Unknown password for Sun box Help!!!

Hello,
My team just adopted a Unix box but the team that turned it over to us didn’t know what the passwords were anymore. The system is setup to do an automatic boot so we are not able to reload the OS so we can configure. WHat can we do so thatwe can log into it. It is useless cause of how it boots from the hard drive only. I don’t have all of the facts but I see them beating themselves up for not knowing it all.