Restore of User Login Domain Controller

My domain layout is (forest domain = hguard.com) and child domain (hgidomain)where all my users login at (hgidomain.hguard.com). I could authoritativelyrestore my forest DC, but when non-authoritatively restoring my child DCI could not add a workstation nor login a user to my child DC where all myuser accounts are located. Cannot find the DC of HGIDOMAIN when the serverwas right there still in workgroup mode as HGINT02.workgroup not HGINT02.HGIDOMAIN.HGUARD.COM. Should I restore my forest as non-authoritative and my child domain as authoritative? Using BE version 9.1 and Server 2000 SP4. After the DR restore mode rebootof HGINT02 (child DC) the system remained in a workgroup not a domain. Suggestionsappreciated.