NT/2000 domain users do not have local administrator privileges

[ATC]

For certain application types this is necessary, for instance some anti-virus program accounts require administrator privileges on the local workstations in order to update themselves, and CD burning software require it to get exclusive access to the media.

[ATC]

IF that user requires local administrator privileges on every single computer in that domain, make him member of the "Domain Administrators" group on the domain controller. This is not a good idea in most cases.

IF the user only requires local administrator privileges on his own computer(s), grant the domain user (E.g.: "MYDOMAIN\JohnDoe") membership in the local "Administrators" group, using the "User Manager" on the workstation(s) in question.