I bought a used PS3. How do I change the account info if I didn't get the other person's password?

Is it possible to delete All information from the system and start from scratch? Or do I need to get the original password?|||there should be an option to format the hard drive or set the system back to default. sorry, i would check, but my ****** is sleeping and she will get mad if i turn the TV on. look it under SYSTEM SETTINGS