Win 98 will not join a Win 2K domain?

I have set up a Win 2K server DC file server and had intended to use the existing Win 98/95 workstations to work within the domain but cannot get them to join. Error indicates no domain is present at login. Win 2K Pro systems join without error and there is no indication of a problem in the event log. Am I missing something? I know this arrangement was possible with Win NT 4.0 and assumed the backwaard compatability with Win 2K. Just to eliminate the obvious I’ve already checked the hardware and lines, and peer to peer works fine.