Computer with Uninterruptible Power Supply Does Not Start After Power Loss Even After AC Power Is Restored

Some computers that have an uninterruptible power supply (UPS) may not start after the UPS shuts off the computer after a power loss, even when the main alternating current (AC) power supply is restored.

This problem occurs when the BIOS setting for system behavior after power restoration is Stay Off, or when the value of the Last State setting is Stay Off. When the BIOS setting is Last State and the system shuts down without pausing at the "It is now safe to power off your computer" message, the value of the Last State setting defaults to Stay Off. When this behavior occurs, the system does not restart even after the power is restored from the UPS.

Note These setting names may not be the same for your computer's BIOS settings. Contact your computer manufacturer for details about the BIOS settings on your computer.

To work around this issue, configure the BIOS settings so that the computer always starts when the AC power supply is restored.

The BIOS of most computers contains the equivalents of the following settings: Always On, Always Off, and Last State in the "After AC Power Supply Fails" section of the BIOS settings. These settings generate the following behaviors when the main AC power supply is restored:

• Always On: The computer starts.
• Always Off: The computer stays off.
• Last State: The computer returns to the last state of AC power.

Note Not all computers have these settings or use the same names for these settings. Contact your computer manufacturer for details about the BIOS settings on your computer.

When a program calls the ExitWindowsEx() function with EWX_SHUTDOWN to shut down the computer, some computers may not start up even after the power is restored from UPS. For additional information, click the following article number to view the article in the Microsoft Knowledge Base: