Here is the back story: I am at a school with a NT4.0 domain server. We bought a new 2003 SP1 server. We have two IP ranges. Our old configuration had static IP address with 2 DNS servers located at the district that was referenced in the TCP/IP properties. I set up the new server with 4 roles. It has an Active Directory. It is a DHCP server (I have 98 machines). The DHCP has a superscope with 2 scopes within the superscope. Each scope has a range of IP address and the exceptions for the server, printers, et cetera. It also is a DNS server that "listens to all IP addresses" instead of listen to the "following IP addresses." However, on the listen to the following IP addresses I put in it's own IP address. The DNS server also has 2 forwarders to the district DNS servers. The last role is as a File Share. I have connected about 400 computers just fine. Everything is working good...however I am now getting sporadic computers that can't log on. I get this message: The computers are still on the server. If I re-add the client machine to the domain, everything is fine--for now. This has been happening to xp machines. It has happened 5 times now, and I am worried about a continual problem or a major problem around the corner. Are there any ideas on what is causing this? I have read up a little bit about SID problems, but I am not that literate yet. I am wondering if I set something up wrong, failed to set something up, or if there is an entirely different reason. Could it be because the computers are still on the NT4.0 directory. I have not taken off the NT4.0 active directory yet or added the NT server to the 2003 server. I also have an independent 2000 server for the library and a 2003 server for a special ed room and program. No one at the district can help. I am out of ideas. I am getting really worried that I did something wrong I can't fix. I am not an expert. I am in the very beginning stages of my MCSA training.