Microsoft KB Archive/842827

= The system may not unload your user profile correctly when you log off from a Windows XP-based computer =

Article ID: 842827

Article Last Modified on 10/25/2007

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APPLIES TO


 * Microsoft Windows XP Home Edition
 * Microsoft Windows XP Professional

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SYMPTOMS
When you log off from a Microsoft Windows XP-based computer, the system may not unload your user profile correctly. Additionally, the following error may be logged in the Application log: Event Type: Error

Event Source: Userenv

Event Category: None

Event ID: 1524

Description:

Windows cannot unload your classes registry file - it is still in use by other applications or services. The file will be unloaded when it is no longer in use.

When you log on to the computer again, the HKEY_CURRENT_USER\Software\Classes registry subkey is not loaded. Additionally, certain COM operations fail. For example, the COM operations for Outlook Forms fails.



CAUSE
This problem occurs because, when you log on to the computer, the WebDav client service caches a handle to the HKEY_CURRENT_USER\Software\Classes registry subkey during per-user initialization.

The HKEY_CURRENT_USER\Software\Classes registry subkey is the Usrclass.dat file in your user profile. The HKEY_CURRENT_USER\Software\Classes registry subkey is used for per-user COM registrations. Therefore, the HKEY_CURRENT_USER\Software\Classes registry subkey cannot be unloaded when you log off from the computer because of the cached handle.



Hotfix information
A supported hotfix is now available from Microsoft. However, it is intended to correct only the problem that is described in this article. Apply it only to systems that are experiencing this specific problem. This hotfix may receive additional testing. Therefore, if you are not severely affected by this problem, we recommend that you wait for the next Windows XP service pack that contains this hotfix.

To resolve this problem immediately, contact Microsoft Customer Support Services to obtain the hotfix. For a complete list of Microsoft Customer Support Services telephone numbers and information about support costs, visit the following Microsoft Web site:

http://support.microsoft.com/contactus/?ws=support

Note In special cases, charges that are ordinarily incurred for support calls may be canceled if a Microsoft Support Professional determines that a specific update will resolve your problem. The usual support costs will apply to additional support questions and issues that do not qualify for the specific update in question.

Prerequisites
You must have Windows XP SP2 installed to apply this hotfix.

Restart requirement
You must restart the computer after you apply this hotfix.

Hotfix replacement information
This hotfix does not replace any other hotfixes.

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.



WORKAROUND
To work around this problem, use the Microsoft User Profile Hive Cleanup Service (UPHClean). UPHClean monitors the computer while Windows is unloading user profiles. UPHClean forces resources that are open to close. Therefore, the computer can unload the user profiles.

To download and install UPHClean, visit the following Microsoft Web site:

http://www.microsoft.com/downloads/details.aspx?FamilyId=1B286E6D-8912-4E18-B570-42470E2F3582



STATUS
Microsoft has confirmed that this is a problem in the Microsoft products that are listed in the &quot;Applies to&quot; section.



MORE INFORMATION
The HKEY_CLASSES_ROOT registry subtree is the merged view of the HKEY_CURRENT_USER\Software\Classes registry subkey and the HKEY_LOCAL_MACHINE\Software\Classes registry subkey. When the system reads from the HKEY_CLASSES_ROOT registry subtree, the per-user data that is located under the HKEY_CURRENT_USER registry subtree overrides the per-computer data that is located under the HKEY_LOCAL_MACHINE registry subtree. If the system writes to the HKEY_CLASSES_ROOT registry subtree, the data is redirected to the HKEY_CURRENT_USER\Software\Classes registry subkey. The HKEY_CURRENT_USER\Software\Classes registry subkey is the Usrclass.dat file in the user’s profile. Therefore, users can create their own COM class registrations because regular users typically have read-only access to the HKEY_LOCAL_MACHINE\Software\Classes registry subkey.

When the problem that is described in this article occurs, the HKEY_CURRENT_USER\Software\Classes registry subkey does not appear in the registry the next time that the user logs on to the computer. Therefore, the per-user COM registrations are missing.

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