Perform a fresh installation of the operating system on another machine (not touching the original disks).If the server performed also other roles, then you might need to modify this procedure to be able to also recover the other roles. This is not a supported method (I'd call it 'experimental') and all supported methods require making backups but you might be able to restore Active Directory Domain Services using the following procedure. How many DCs do you have in your environment? If the failed server was not the only DC in the domain, then there are other ways to restore the server.
