I have a SBS 2003 network with about 30 computers. I just finished upgrading the server box this weekend. I have manage to connect all the computers and users back to the network just fine except one. I have a machine running XP pro that does not connect to the server. I am able to see, traceroute, and ping the server but I keep getting the "unable to connect to server...working offline" error. I tried removing it from the domain and getting it back on the domain and that does not work. I have remove the firewall, and that does not work. Removed the computer from AD, change the computer name locally and at the server then added the computer back again under different name and that did not work. Finally I decided to allow "trust delegation" for that machine and that seems to work. I would really like to find out what the problem is and not have to set "trust delegation" on the machine. Any ideas?