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After you add the CopyFileBufferedSynchronousIo registry entry in Windows Vista, a file copies only slightly more quickly when you use Windows Explorer to copy the file to another computer

Important This article contains information about how to modify the registry. Make sure that you back up the registry before you modify it. Make sure that you know how to restore the registry if a problem occurs. For more information about how to back up, restore, and modify the registry, click the following article number to view the article in the Microsoft Knowledge Base:
256986 Description of the Microsoft Windows registry
In Windows Vista, you add the CopyFileBufferedSynchronousIo registry entry to improve the speed of a file copy operation. However, when you use Windows Explorer to copy a file from the Windows Vista-based computer to a computer that is running an older Windows operating system, the file copies only slightly more quickly.

Note The file copies more quickly if you use a command-line tool to copy the file. You can use command-line tools such as Robocopy.exe and Xcopy.exe to copy the file.
This problem occurs because Windows Explorer does not check for the CopyFileBufferedSynchronousIo registry entry.

In Windows Vista, the CopyFile function creates a non-cached I/O request to perform a write operation. Therefore, the speed of the file copy operation is affected by the disk speed and by other resources on the older operating system.

The CopyFileBufferedSynchronousIo registry entry reverts the CopyFile function in Windows Vista to its earlier behavior. After you add the registry entry, you expect the CopyFile function to work as it would in an earlier Windows operating system. However, because Windows Explorer does not check for this registry entry, this problem occurs.

Service pack information

To resolve this problem, obtain the latest service pack for Windows Vista. For more information, click the following article number to view the article in the Microsoft Knowledge Base:
935791 How to obtain the latest Windows Vista service pack
To resolve this problem, apply the following hotfix. After you apply this hotfix, Windows Explorer checks for the CopyFileBufferedSynchronousIo registry entry.

Note This hotfix takes effect only if you add the CopyFileBufferedSynchronousIo registry entry and set its value to 1.

Hotfix information

A supported hotfix is available from Microsoft. However, this hotfix is intended to correct only the problem that is described in this article. Apply this hotfix only to systems that are experiencing this specific problem. This hotfix might receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next software update that contains this hotfix.

If the hotfix is available for download, there is a "Hotfix download available" section at the top of this Knowledge Base article. If this section does not appear, contact Microsoft Customer Service and Support to obtain the hotfix.

Note If additional issues occur or if any troubleshooting is required, you might have to create a separate service request. The usual support costs will apply to additional support questions and issues that do not qualify for this specific hotfix. For a complete list of Microsoft Customer Service and Support telephone numbers or to create a separate service request, visit the following Microsoft Web site: Note The "Hotfix download available" form displays the languages for which the hotfix is available. If you do not see your language, it is because a hotfix is not available for that language.


No prerequisites are required.

Restart requirement

You have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace any other hotfixes.

Registry information

To use one of the hotfixes in this package, you do not have to make any changes to the registry.

File information

The English version of this hotfix has the file attributes (or later file attributes) that are listed in the following table. The dates and times for these files are listed in Coordinated Universal Time (UTC). When you view the file information, it is converted to local time. To find the difference between UTC and local time, use the Time Zone tab in the Date and Time item in Control Panel.
Windows Vista, 32-bit versions
File nameFile versionFile sizeDateTimePlatform
Update.mumNot applicable26,83821-Aug-200720:40Not applicable
X86_microsoft-windows-shell32_31bf3856ad364e35_6.0.6000.20664_none_6a8fa8bd2e200c73.manifestNot applicable975,77221-Aug-200720:40Not applicable
Shell32-ppdlic.xrm-msNot applicable3,15021-Aug-200703:44Not applicable
Windows Vista, 64-bit versions
File nameFile versionFile sizeDateTimePlatform
Amd64_microsoft-windows-shell32_31bf3856ad364e35_6.0.6000.20664_none_c6ae4440e67d7da9.manifestNot applicable977,91921-Aug-200720:46Not applicable
Update.mumNot applicable27,34721-Aug-200720:40Not applicable
Wow64_microsoft-windows-shell32_31bf3856ad364e35_6.0.6000.20664_none_d102ee931ade3fa4.manifestNot applicable968,81921-Aug-200720:46Not applicable
Shell32-ppdlic.xrm-msNot applicable3,15021-Aug-200704:45Not applicable
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. This problem was first corrected in Windows Vista Service Pack 1.
Warning Serious problems might occur if you modify the registry incorrectly by using Registry Editor or by using another method. These problems might require that you reinstall the operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

To add the CopyFileBufferedSynchronousIo registry entry, follow these steps:
  1. Click Start, type regedit in the Start Search box, and then press ENTER.
  2. Locate and then click the following registry subkey:
  3. On the Edit menu, point to New, and then click DWORD Value.
  4. Type CopyFileBufferedSynchronousIo to name the new entry, and then press ENTER.
  5. Right-click CopyFileBufferedSynchronousIo, and then click Modify.
  6. In the Value data box, type 1, and then click OK.
  7. Exit Registry Editor.
For more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:
824684Description of the standard terminology that is used to describe Microsoft software updates

Article ID: 941673 - Last Review: 10/08/2011 14:47:00 - Revision: 3.0

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