Home Folder Mapping

In my computer lab I recently upgraded several of the computers from Windows 2000 to Windows XP. The server is Windows 2000 w/ Active Dir. The user account properties in map users home folders (Drive Z:) to \\ServerName\Users\%username%. This worked fine when the client computers were running Windows 2000. Since installing Windows XP Z: is now mapping to \\ServerName\Users where users see the entire list of user folders. For various reasons, users need Z: to continue mapping to their folderand not the Users folder. They are still able to get a correct mapping on computers that are running Windows 2000. Any idea how I can get them mapping correctly again?