The System log reports many "PerfOS event ID: 2001" errors when you use a Microsoft Windows Server 2003-based or Windows Server 2008-based computer that has more than 32 processors

When you use a Microsoft Windows Server 2003 or Microsoft Windows Server 2008-based computer that has more than 32 processors, you may notice that many events are reported in the System log that resemble the following:

This problem occurs because one or more 32-bit applications have used the NtQuerySystemInformation function in order to determine the number of processors that are available for the computer. If more than 32 processors are available, the PerfOS event is logged every time that the NtQuerySystemInformation function is used.

Windows Server 2003-based computers that are running Service Pack 2 (SP2)

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 your operating system. Microsoft cannot guarantee that these problems can be solved. Modify the registry at your own risk.

This problem was addressed in Windows Server 2003 Service Pack 2 (SP2). You do not have to download a hotfix to resolve this problem. However, some Windows registry information is missing. To resolve this problem, you must modify the Windows registry. To do this, follow these steps:

1. Click Start, click Run, type regedit, and then click OK.
2. Locate and then click the following registry key:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\PerfOS\Performance
3. In the Edit menu, point to New, click DWORD Value, type LogErrorToFile, and then press ENTER.
4. Double-click LogErrorToFile, type 0, and then click OK.
   Note When you set the LogErrorToFile value to 0, PerfOS events are no longer logged in the System log. You can enable logging again by setting this value to 1.

Hotfix information

Service pack information for Windows Server 2003

To resolve this problem, obtain the latest service pack for Windows Server 2003. For more information, click the following article number to view the article in the Microsoft Knowledge Base: 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.

Windows Server 2003-based computers that are running Service Pack 1 (SP1) or earlier versions

When you install this hotfix on computers that are running Service Pack 1 (SP1) or earlier versions, you do not have to modify the registry to resolve this problem.

Prerequisites

There are no prerequisites for installing this hotfix.

Restart requirement

You must restart your 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.

Windows Server 2003, Itanium-based computers that are running SP1 or earlier versionsWindows Server 2003, x64-based computers that are running SP1 or earlier versionsWindows Server 2003, x86-based computers that are running SP1 or earlier versions

Service pack information for Windows Server 2008

Note This bug is fixed when you install this hotfix on Windows Server 2008 or on Windows Server 2008 SP2. Therefore, you do not have to modify the registry entry on Windows Server 2008 or on Windows Server 2008 SP2.

Prerequisites

There are no prerequisites for installing this hotfix.

Restart requirement

You must restart your 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.

Windows Server 2008, Itanium-based computers
Windows Server 2008, x64-based computers
Windows Server 2008, x86-based computers

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 Server 2003 Service Pack 2.

For more information, click the following article number to view the article in the Microsoft Knowledge Base: