Windows 2000 Professional workgroups

We are running a wide area network and are in the process of migrating to windows 2000. The problem is how do we do the transition without losing our current configuration of workgroups at the local level. Currently what we have are win98 clients that authenticate through the domain, but are members of the local workgroup. It appears that with windows 2000 you can not do this any longer. You now have to join a domain. does anyone know how to get around this?