registering pc on network

we got a server on the domain education. we took 3pcs out (not off the network) and replaced them with win 2000 pcs. Ive tried to put the new machines on the network, by using the existing pc name and also user name and p/w. the pc is on the domain education. when you try to log on using the user name and p/w, error msg is “your account is configured to prevent you from using this computer.please try another.