Microsoft KB Archive/290095

= APM Laptop Computer on Battery Power Uses AC Power Policy =

Article ID: 290095

Article Last Modified on 1/31/2007

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APPLIES TO


 * Microsoft Windows 98 Standard Edition
 * Microsoft Windows 98 Second Edition
 * Microsoft Windows Millennium Edition

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This article was previously published under Q290095



SYMPTOMS
When you are running your laptop computer that is equipped with an Advanced Power Management-enabled basic input/output system (BIOS) on battery power, your computer may enter Standby or Hibernate mode, as if it is connected to an AC power source.



CAUSE
This problem can occur only if all of the following conditions exist:
 * The Power Meter icon is not visible on the taskbar.
 * The battery is not detected by the virtual power device driver (Vpowerd.vxd) during device initialization, which can occur under either of the following conditions:
 * The computer was started on AC power after the battery was physically removed from the battery slot, and the battery is installed after the operating system is fully initialized.
 * The computer was started on AC power with the battery physically installed in the battery slot, and the APM BIOS does not indicate battery presence during the system initialization.

Vpowerd.vxd does not dynamically create and destroy APM battery devices when batteries are inserted or removed. Batteries that are not detected during initialization are never sensed by the power management drivers. This prevents the system power management drivers from being notified of a switch to battery power, which results in the DC power policy never being applied. The power policy refers to the standby and hibernate thresholds for the power scheme when running on the battery.



RESOLUTION
If your computer BIOS also supports Advanced Configuration and Power Interface (ACPI), you can enable ACPI to eliminate the problem.

To work around this problem, enable the Power Meter:
 * 1) Click Start, point to Settings, click Control Panel, and then double-click Power Management or Power Options.
 * 2) Click the Advanced tab, and make sure that the Always show icon in the taskbar check box is checked.

The Power Meter handles the required WM_POWERBROADCAST / PBT_APMPOWERSTATUSCHANGE power broadcast messages, interacting with the APM battery device or devices, which causes the battery presence to be made known to system power management drivers.



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed at the beginning of this article.

Additional query words: irp

Keywords: kbnofix kbprb KB290095

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