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Power management configuration in Windows 2000, Windows XP, and Windows Server 2003 is based on the concept of power schemes. A power scheme is a group of preset power options that are passed to the Power Policy Manager component of the operating system to control the machine’s power-management behavior.

Each power scheme consists of a global power-policy structure and a power-policy structure.

• Global power-policy structures contain preset power options that are global across all power schemes.
• Non-global power-policy structures contain power options that are unique to a particular power scheme.

These power-policy structures are further divided into machine structures and user structures.

• Values in machine structures are stored in the HKEY_LOCAL_MACHINE registry key, and none of these values are exposed in the user interface. For example, you can’t set any of these values using the Power Options applet in the Control Panel.
• Values in user structures are stored in the HKEY_CURRENT_USER registry key and some of these values are displayed in the user interface. Some of these parameters can be set using the Power Options applet in Control Panel.

The data structures defining power management policy are listed below:

• GLOBAL_POWER_POLICY – used to manage global power policies. This structure contains the data common to all power schemes. This structure is a container for a GLOBAL_USER_POWER_POLICY structure and a GLOBAL_MACHINE_POWER_POLICY structure, which contains elements that are read from and written to the registry.
• GLOBAL_MACHINE_POWER_POLICY – this structure is a part of the GLOBAL_POWER_POLICY structure. It contains the data common to all power schemes and users. The elements in this structure are read from and written to the HKLM key in the registry.
• GLOBAL_USER_POWER_POLICY – this structure is a part of the GLOBAL_POWER_POLICY structure. It contains the data common to all power schemes for the user. The elements in this structure are read from and written to the HKCU key in the registry.
• POWER_POLICY – used to manage non-global power policies. This structure contains the data unique for all power schemes. This structure is a container for the USER_POWER_POLICY and MACHINE_POWER_POLICY structures that contain the elements to be read from and written to the registry. There is one POWER_POLICY structure for each power scheme on a machine.
• MACHINE_POWER_POLICY – this structure is a part of the POWER_POLICY structure. It contains the data unique to each power scheme, but common to all users. The elements in this structure are read from and written to the HKLM key in the registry.
• USER_POWER_POLICY – this structure is a part of the POWER_POLICY structure. It contains the data unique to each user and power scheme. The elements in this structure are read from and written to the HKCU key in the registry.