JSI Tip 10079. Naming conventions in Active Directory for computers, domains, sites, and OUs.

Microsoft Knowledge Base Article 909264 contains the following introduction:

This article describes the naming conventions for computer accounts in Microsoft Windows, NetBIOS domain names, DNS domain names, Active Directory sites, and organizational units (OUs) that are defined in the Active Directory directory service. The topics that are discussed include the valid characters for names, the minimum and maximum name lengths, reserved names, names that we do not recommend, and general recommendations that are based on supporting Active Directory in small, medium, and large deployments.