Windows operating systems traditionally function in one of two network models. Which model does not operate using centralized user accounts?

The correct answer is the workgroup model. In a workgroup network environment, each computer operates independently, and there is no centralized management for user accounts. This means that user accounts are created and maintained on each individual machine, making it suited for small networks where centralized control is not required.

In contrast, the domain model relies on a centralized server to manage user accounts, permissions, and policies. This centralization allows for easier management of resources and users across multiple computers. Active Directory is a specific implementation of the domain model, providing a directory service to manage network resources, users, and security. As for user groups, this term refers to a method of organizing users within networks but does not represent a specific network model.

The distinction lies in how user accounts are managed: a workgroup has no centralized user account handling, while domains and Active Directory do. This fundamental difference is what makes the workgroup model the correct choice for the question.