In January there was a post titled "Unable to join domain (Samba PDC)" ( http://social.technet.microsoft.com/Forums/en-US/w7itpronetworking/thread/94c66fbd-4e4e-4e78-bc9d-55ef64c7551f/ ). That article pointed the same question on the Samba mailing list - http://lists.samba.org/archive/samba-technical/2009-January/062827.html where an employee from Microsoft responded via a third party (allegedly):"Jim Pinkerton asked me to post this message from Microsoft: Sincere apologies, but wanted to confirm that there is an issue with NT Domain support in Windows 7. We're trying to expeditiously track down exactly the issue(s), but the short of it is I wouldn't spend time trying to get this functionality to work. We'll get some sort of official notice out shortly (and I do mean shortly). Jim Pinkerton MicrosoftIs there any additional update on this? It seems like rather late in the game to still have this issue in a release candidate.Best Regards,Loren

Many have been having success with Samba by updating it. Have you tried?