My service tag is DCNXK91-595B i can't get into it as it has me locked out and I don't know the administator password. How do I get by this problem. I need the master password so I can fix my computer

The Administrator Password on Dell systems is usually the same as the one used by the main user of the computer, provided their account is a member of the administrator group. (i.e. an administrator and not a limited user)

I know this works for getting into the Recovery Console on Windows XP machines, not sure if it works for getting into the actual "Administrator" log-in in XP.