No logon server available

I need help. I would like to correct this error message and also understand what is causing this problem.
Server = w2k; computers 1,2 have w2k and computer#3 has XP. Computers 1 & 2 have intel 850gbl motherboards with P4 and computer 3 is laptor. server has STL2 board.
connection is via a 10/100 hub. Computer1&2 can ping server. Computer #3 and server can ping each other and share files.If server pings computer 1&2 I get timed out. Computer 1&2 can ping server. Ipconfig/all reports all similar except Node Type is Hybird for server & xp computer while computer 1 & 2 have broadcast node types. Problem from server I cannot connect to computer 1 & 2 to share files.
When I click on them I get "no logon server available".
I need a step by step solution and a conceptual understanding of what I did wrong.Network is my lab network which I built to learn about w2k networking. I can't find any information in books about No Logon Server and how to test to see if network is set up correctly. Ican't find any ipconfig command that will show up the problem. I have loaded active directory a few times I have unplugged all connections and same error message keeps comming up. IP is static.Dns is working.