windows 2003 DC restore

Hallow,

After a 2003 server crash (secondary DC) we restored it from a 2 weeks old system disk image backup. The first DC sees it as duplicate and all the authentication regarding this server fails. Also fails the DC replication. There are a lot of shares and printers on it, how can we resolve the Kerberos authentication problem and save the DC information in order not to reinstall it (or demote/remove/insert/promote)?
What is the right system backup solution for a DC?

Any suggestion is welcome, thanks in advance.