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Power Options\windows\system\powercfg.cpl

Control Windows' support for Advanced Power Management (APM).

To Open

Control Panel [Performance and Maintenance] Power Options

Command Prompt powercfg.cpl


Advanced Power Management relies on cooperation between your computer's BIOS and operating system. APM covers everything from your computer's power switch to the power-saving features that reduce power consumption or extend the life of your computer's battery (see Figure 4-71).

Figure 4-71. The Power Options window lets you configure the various power-saving features of your computer

Before you mess with any settings here, make sure that APM support is enabled in your system BIOS. For best results, enable the main "APM support" option, but disable all APM options in your BIOS. Refer to the documentation that came with your computer or motherboard for details. Settings in this window are divided into the following tabs:

Power Schemes

The Power schemes listbox allows you to save your power management settings into one or more schemes, much like Themes (see Display Properties) and Sound Schemes (see Hibernate). Click Save As to create a new scheme or Delete to remove the currently selected scheme.

The Settings below allow you set timed power-saving features for the currently selected scheme. Note that not all computers support the System standby and System hibernates features; even those that claim to may not do it very well. If your computer crashes coming out of standby or hibernation mode (see Sounds and Audio Devices below), or simply doesn't come out at all, check with your computer or motherboard manufacturer for a BIOS update.


The settings on this page are pretty self-explanatory. See Hibernate, below, for details on the hibernation feature.


Hibernation, also known as "Instant On," allows you to completely shut off your computer and then turn it back on later (and resume work in seconds as though it was never shut off). It does this by saving an image of your system's memory into a file called hiberfil.sys, located in the root directory of your windows drive (usually C:\); when the computer comes out of hibernation, the file is read back into memory and your previous session is restored, all without having to reload Windows or any of your applications.


Windows XP includes built-in support for Un-interruptible Power Supplies (UPSs), which keep your computer running in the event of a power outage or other disruption. Depending on the capacity of your UPS, you may have anywhere from a few minutes to a half hour to save your work and shut down your computer gracefully. A UPS is a good investment if you live in a stormy climate or other area where power interruptions are frequent.

Although a UPS doesn't really have to interact with Windows at all, support configured through this dialog enables some advanced features, such as monitoring tools that alert you when a power outage has occurred and inform you of how much power is left in the UPS battery.


All settings in this dialog are also covered in Chapter 5.

See Also

Control Panel

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