Slow logon to domain

We have two XP pro and two Win2K PC’s that take on average 10mins to log in to the server. The win98 pc’s are fine. I have edited the group policy setting for “always wait for the network at startup” to enable as recommended by various websites. I have also tried adding our servers IP address to the Hosts file. Neither of which has speeded up the login.
Does anyone have any other suggestions?