The KB article isn't likely your issue.

Sounds like you're letting the users build their XP machines. Have them join or create a Workgroup during setup. Create the machine account, then have them do System Properties -> Computer Name -> Change. They will be prompted for a local account with sufficient rights to join the domain (even if they are already logged in as Administrator). Type it in, hit ok a few times, reboot, viola.

-Bryce