Small system - 2 Windows 2000 servers (PDC and Sql Server) and 2 Windows 2003 servers (2nd DC and print server and 2nd SQL server) - 50 clients Windows XP Pro SP2 and 6 still Windows 2000 Pro awaiting conversion. All patches are up to date. Using DNS and active directory, NetBIOS is deprecated and WINS is disabbled, 'Computer Browser' disabled server and clients. In the last three weeks I have had the above error when trying to join computers to the domain, demote a test DC, and add services to the 2k3 server. WHY? I have been to the MS knowledgebase and Google repeatedly and not had much luck in resolving this issue. Only quick fix I have found is to restart the the PDC. NOT acceptable! Careful review did not find any evidence of 'epdump', the only malware reference I had run accross. I am now looking at the various 'registry entries'. Has anybody tried the 'kill/rebuild' DNS recommendation? How much pain is involved?