Windows NT contains three kinds of built-in groups:
In Windows 2000, the built-in groups are similar in function, except that a fourth type, called a domain local group, is also available. Built-in groups in Windows 2000 are also administered differently using different tools. Also, system groups in Windows 2000 are referred to as built-in identities.
You cannot rename or delete a built-in group, and you cannot change the membership of a system group.