Users in the Domain Users group do not have permission to log on to the server locally, meaning that they can't log on to the server at the console. They can still access the server's resources across the LAN, however. If you want the user to be able to log on to the server while sitting at the console, give the user the Log on Locally right. The article Q234237 in Microsoft?s Knowledge Base provides step-by-step instructions for giving users this right.
This was first published in March 2002