When you copy large files to or from earlier operating systems, the copy operation may be slower than expected on some Windows Vista-based computers

Consider the following scenario:

• On a Windows Vista-based computer, you copy files to or from another computer on a network.
• This other computer is a Windows XP-based computer or a Windows Server 2003-based computer.
• These files are each 100 megabytes (MB) or larger.
• You use Windows Explorer to copy the files. For example, you use a drag-and-drop operation in Windows Explorer to copy the files.

In this scenario, the file transfer operation is slightly slower than expected. This problem occurs only in certain hardware configurations. This problem does not occur when you copy files to or from another Windows Vista-based computer.

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:

To work around this problem, you may be able to use one of the following methods to improve the speed of large file transfers:

Method 1: Disable the Windows Explorer Navigation Pane

To disable the Windows Explorer Navigation Pane, follow these steps:

1. Click Start
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   , and then click Computer.
2. Click Organize, point to Layout, and then click Navigation Pane.

Method 2: Map a network drive

Map a network drive to the folder that contains the files that you want to copy. To do this, use one of the following methods:

Method A: Use the Windows user interface

1. Click Start
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   , right-click Computer, and then click Map Network Drive.
2. Type the path of the network folder in the Folder box, and then click Finish. For example, type \\computer_name\shared_folder_name, and then click Finish.

Method B: Start a command prompt, and then map the drive by using net use command

1. Click Start
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   , type cmd in the Start Search box, and then click cmd in the Programs list.
2. Type Net use x:\\computer_name\shared_folder_name, where x: is the letter of the drive that you want to assign to the shared resource.
3. Press ENTER.

Method 3: Use Robocopy

Use the Robocopy utility that is included with Windows Vista to copy the files. For example, type the following command at a command prompt, and then press ENTER: For more information about how to use Robocopy, type Robocopy /? at a command prompt, and then press ENTER.

Method 4: Disable the automatic adjustment for the TCP window size on the network

Method A

To have us disable auto-tuning for you, go to the "Fix it for me" section. If you would rather disable auto-tuning yourself, go to the "Let me fix it myself" section.

Fix it for me

To disable auto-tuning automatically, click the Fix this problem link. Then click Run in the File Download dialog box, and follow the steps in this wizard.

Fix this problem

Note This wizard is temporarily in English only. However, the automatic fix also works for other language versions of Windows.

Note If you are not on the computer that has the problem, you can save the automatic fix to a flash drive or to a CD, and then you can run it on the computer that has the problem.

We would appreciate your feedback. To provide feedback or to report any issues with this solution, please leave a comment on the "Fix it for me" blog (http://blogs.technet.com/fixit4me/) , or send us an e-mail (mailto:fixit4me@microsoft.com?Subject=KB932170 - Disable TCP auto-tuning) message.

Let me fix it myself

1. Click Start
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   , click All Programs, and then click Accessories.
2. Right-click Command Prompt, and then click Run as Administrator.
   
   
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   If you are prompted for an administrator password or for confirmation, type your password, or click Continue.
3. At the command prompt, type the following command, and then press ENTER:
   netsh interface tcp set global autotuninglevel=disabled
4. Exit the Command Prompt window.
5. Restart the computer.

For more information, visit the following Microsoft Web site:

Method B

Enable the "offload checksum" function of the network adapter. For information about how to do this, contact the manufacturer of the network adapter. For information about how to contact the manufacturer of the network adapter, visit the following Microsoft Web site: Microsoft provides third-party contact information to help you find technical support. This contact information may change without notice. Microsoft does not guarantee the accuracy of this third-party contact information.

For more information about the meaning of the offload checksum, visit the following Microsoft Web site:

Check whether the problem is fixed. If the problem is fixed, you are finished with this article. If the problem is not fixed, you can contact support (http://support.microsoft.com/contactus) .

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section. This problem was corrected in Windows Vista Service Pack 1.