PDC has turned into a WORKSTATION.!

One of my domains has 1 PDC & BDC,which are both NT4 Servers.Also in the domain are 30 NT4 Workstations.Arriving one morning after some leave,my PDC had become a workstation in the domain,even though everything seemed ok.Meanwhile my BDC had taken over as PDC,since it no longer found it’s original PDC.Even though i had backups,it did not go back.
Apparently there was a powercut during the night,but nothing was revealed in the Log.

Is there a way to resolve this problem.
Many thanks in advance.