Windows Explorer may crash when you try to expand a parent folder in the Windows Explorer navigation pane in Windows Vista or in Windows Server 2008

On a Windows Vista or Windows Server 2008-based computer, you have a folder that contains many layers of subfolders. Each subfolder contains only one subfolder. When you try to expand the parent folder in the Windows Explorer navigation pane, Windows Explorer expands the folder to the last level of the subfolders as long as each subfolder contains only one subfolder. This problem may cause Windows Explorer to crash if there are many layers of subfolders.

If you have a subfolder that contains two or more subfolders, Windows Explorer stops expanding the folders when it reaches the folder that contains the two subfolders. For example, you have the following folder tree:

• C:\temp
  • C:\temp\1
    • C:\temp\1\2
      • C:\temp\1\2\3
        • C:\temp\1\2\3\4
          • C:\temp\1\2\3\4\4a
          • C:\temp\1\2\3\4\4b

When you click the triangular icon to expand the C:\temp folder, Windows Explorer expands all the way to the C:\temp\1\2\3\4 folder. Windows Explorer does not expand the subfolders inside the C:\temp\1\2\3\4 folder because that folder has two subfolders, 4a and 4b.

Note This problem does not occur in Windows operating systems that are earlier than Windows Vista.

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 the problem described in this article. 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.

Important Windows Vista and Windows Server 2008 hotfixes are included in the same packages. However, only one of these products may be listed on the �Hotfix Request� page. To request the hotfix package that applies to both Windows Vista and Windows Server 2008, just select the product that is listed on the page.

Prerequisites

To apply this hotfix on a Windows Vista-based computer, you must have Windows Vista SP1 installed. For more information, click the following article number to view the article in the Microsoft Knowledge Base: There are no prerequisites for Windows Server 2008-based computers.

Restart requirement

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

Hotfix replacement information

This hotfix does not replace a previously released hotfix.

Registry information

Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base: After you install this hotfix, you have to make the following changes to the registry to set the value of the DoNotExpandSingletons registry entry to 1:

1. Click Start, type regedit in the Start search box, and then press ENTER.
   If you are prompted for an administrator password or for confirmation, type the password, or provide confirmation.
2. Locate and then expand the following registry subkey:
   HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Explorer\Advanced
3. On the Edit menu, point to New, and then click DWORD (32-bit) Value.
4. Type DoNotExpandSingletons, and then press ENTER.
5. Right-click DoNotExpandSingletons, and then click Modify.
6. In the Edit DWORD (32-bit) Value box, type 1 in the Value data box, and then click OK.
7. Exit Registry Editor.
8. Restart the computer.

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 and Windows Server 2008 file information notes

The .manifest files and the .mum files that are installed in each environment are listed separately in the "Additional file information for Windows Server 2008 and for Windows Vista" section. These files and their associated .cat (security catalog) files are critical to maintaining the state of the updated component. The .cat files are signed with a Microsoft digital signature. The attributes of these security files are not listed.

For all supported x86-based versions of Windows Server 2008 and of Windows Vista

For all supported x64-based versions of Windows Server 2008 and of Windows Vista

For all supported IA-64-based versions of Windows Server 2008

Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the "Applies to" section.

Additional file information for Windows Server 2008 and Windows Vista

Additional files for all supported x86-based versions of Windows Server 2008 and of Windows Vista

Additional files for all supported x64-based versions of Windows Server 2008 and of Windows Vista

Additional files for all supported IA-64-based versions of Windows Server 2008