A long environment variable is truncated to 1024 characters the next time that you log on to Windows Vista

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When you specify a long environment variable in Windows Vista, the environment variable is truncated to 1024 characters the next time that you log on.
This problem occurs because the buffer that the Winlogon.exe process uses to manipulate the environment variable is limited. When Winlogon.exe creates other processes, the process environment blocks of these processes truncate environment variables to 1024 characters.

Note By default, you can create environment variables up to 2048 characters long in Windows Vista.

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

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.


There are no prerequisites for installing this hotfix package.

Restart requirement

You do not have to restart the computer after you apply this hotfix.

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

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
Windows Vista, 64-bit versions
File nameFile versionFile sizeDateTimePlatform
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.
More information
For more information about the terms that are used to describe software updates, click the following article number to view the article in the Microsoft Knowledge Base:
824684 Description of the standard terminology that is used to describe Microsoft software updates

Article ID: 935765 - Last Review: 01/16/2015 17:15:06 - Revision: 5.0

Windows Vista Home Basic, Windows Vista Home Premium, Windows Vista Ultimate, Windows Vista Business, Windows Vista Enterprise

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