CHANGING THE WORKGROUP NAME STOPS DIAL-UP NETWORKING AUTHENTICATION

If you change the Workgroup Name on a Windows 9x computer (right click Network Neighborhood | Properties | Identification Tab), you may find that, following a reboot, Dial-Up Networking "connectoids" do not authenticate with usernames and passwords as they did previously. Connectoids are the connection settings you save as icons in the Dial-Up Networking folder.

This can happen, for example, if the computer you are dialing in to is a Windows NT Server using Microsoft Challenge Handshake Authentication Protocol (MSCHAP) to authenticate callers. When the Windows 98 client supplies a username and password but no domain name is supplied, Windows supplies the Workgroup name instead. Because Windows also caches the logon credentials for a connectoid, once a Workgroup name has been changed, the new credentials (with the new Workgroup name) and the cached credentials no longer match up.
Microsoft says that this is by design. To work around the problem, simply reenter the username and password for each connectoid that was created prior to the Workgroup name change.