Which settings control the actions of a computer when it is left alone for a while?

The correct choice pertains to Power Settings because these settings dictate how a computer behaves during periods of inactivity, which includes actions such as dimming the display, entering sleep mode, or shutting down after a designated period. Power Settings are essential for managing energy consumption and extending the longevity of equipment by reducing the usage of resources when the computer is not actively in use.

Display Preferences primarily focus on settings related to screen resolution, brightness, and how the display interacts during use, but they do not control the overall power management behaviors of the system.

Network Configuration pertains to how a computer connects to networks. While it ensures that network connectivity is maintained or modified when in use, it does not affect how the computer behaves when it is left idle.

User Preferences are tailored to individual user settings related to application behavior, personalization, or interface, but again, they do not specifically manage the power-related actions that occur when the system is unattended.

Thus, Power Settings are crucial for defining what the computer does when it is left idle, making this the most suitable choice for the question.