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.
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.
You have to restart the computer after you apply this hotfix.
Hotfix replacement information
This hotfix does not replace any other hotfixes.
To use one of the hotfixes in this package, you do not have to make any changes to the registry.
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.
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:
Click Start, type regedit in the Start Search box, and then press ENTER.
Locate and then click the following registry subkey:
Windows Vista Home Premium, Windows Vista Ultimate, Windows Vista Business, Windows Vista Home Premium 64-bit Edition, Windows Vista Ultimate 64-bit Edition, Windows Vista Business 64-bit Edition, Windows Vista Enterprise 64-bit Edition