Microsoft KB Archive/150009

= WinNT System Shutdown/Power Off Causes Boot-Sector Corruption =

Article ID: 150009

Article Last Modified on 11/1/2006

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APPLIES TO


 * Microsoft Windows NT Advanced Server 3.1
 * Microsoft Windows NT Workstation 3.1
 * Microsoft Windows NT Advanced Server 3.1
 * Microsoft Windows NT Workstation 3.5
 * Microsoft Windows NT Workstation 3.51
 * Microsoft Windows NT Server 3.5
 * Microsoft Windows NT Server 3.51

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This article was previously published under Q150009





SYMPTOMS
If you have Windows NT installed on a partition using the FAT file system, the boot sector may become corrupted after performing a shutdown.

After you indicate you want to shut down Windows NT, the operating system begins closing applications and network connections and performing file- system shutdown functions. During this last process you will see the message:

  Please wait while the system writes unsaved data to the disk

As soon as the status is returned that each of these functions has been completed, Windows NT displays the following message:

  It is now safe to turn off your computer.

If you immediately turn off your computer, disk corruption may occur that can prevent the computer from restarting.



CAUSE
The operating system thinks the file-system shutdown functions have completed successfully, but there is still an asynchronous thread running that has not yet completed its I/O to the volume. This process is used to mark the volume clean by updating information on the disk. If the computer is powered off while this last write is in progress, disk corruption may occur.



RESOLUTION
If you look closely at the disk access light of a drive running Windows NT and using the FAT file system, you will see that approximately 7 seconds after the message is posted stating it is safe to turn off the computer, further disk activity takes place on the drive.

To prevent disk corruption, wait for approximately 10 seconds after the last message is posted--or observe the disk access light and wait for the last write to take place--before you turn off the computer.

This behavior occurs only on partitions formatted using the FAT file system; partitions formatted using the NTFS file system do not exhibit this problem.



STATUS
Microsoft has confirmed this to be a problem in Windows NT versions 3.1, 3.5, and 3.51. This problem was corrected in the latest Windows NT 3.51 U.S. Service Pack. For information on obtaining the Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K

Keywords: KB150009

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