In Active Directory Sites and Services, you are only given one site to start with. If you have two locations that are geographically separated by a WAN, both of those site's objects will be in the same site unless you set things up correctly.
If you don't change the default settings, you could have users in the remote location authenticating to your local domain controller (DC), and vice-versa. With intricate login scripts, this can be a disaster.
In Active Directory Sites and Services, create a new site for each physical location that you have (right-click Sites, select New Site).
Additionally, create a subnetfor each logical subnet that you have (right-click Subnets, select New Subnet). After creating these subnets, make sure that you associate them with the appropriate site.
Finally, move your servers from the default site that was created to the new site containers that you have created. Make sure that these servers live in a subnet that is associated with that site. This will ensure that your Win2k clients, as well as your Win9x clients, go to a local DC when they attempt to authenticate.
This happens because clients query AD-DNS for a DC that is local to their own local IP subnet. If your servers are in sites that are associated with subnets, this happens quickly and efficiently, and you never have Chicago clients knocking on the door of a New York domain controller.