Very odd problem. XP clients are unable to logon to the domain "domain not available". I found the problem to be with XP's default policy "Domain member: Digitally encrypt or sign secure channel data (always)is set to enabled. NT by default is set to disable but you can add the RequireSignOrSeal registry key and set it to one to enable this but that would cause a problem with 9x and 2k machines. Here is the odd thing. I can add that key to the PDC but not to any BDC because when I restart the netlogon service on a bdc I get an access denied. I set the PDC back to default 0 then XP computers cant logon unless I stop the the netlogon service on the PDC forcing clients to use a BDC which then have no problem authenticating the clients. odd. If I disable the policy on the XP clients then they authenticate no problem. How can the BDC authenicate the XP cleints but the PDC cant even though neither requires sign or seal? ...any ideas??