Lost SBS 2003 Administrator password on Active Directory

Hello,
I have been looking for a solution for this issue for the past week without success.
A client of mine has a server with SBS 2003 but has no way of finding out what the admin password is.
I have tried many technics trying to utilise local admin account login but the policy on this server prohibits access to this account (even on active directory restore mode).
PLEASE HELP!
this has become urgent as the DHCP server is down all of a sudden.
Any hint is welcome.
Thank you!