BDC can’t join the domain

I installed a BDC on my NT4.0 network and it crashed after a day because of a hardware problem. I’ve fixed the hardware problem, reloaded the WINNT 4.0 setup but it will not let me join the domain. I’ve removed the BDC from Server Manager on the PDC, stopped the replication I think! and rebooted the PDC. The error message I get is, “The domain controller for this domain cannot be located”. I install win98 on this system and it joins the domain fine with the same hardware and as I’ve mentioned this was a BDC for a day! Is there a registry change that needs to be made to the sam database?Hope you can help. Thanks alex