When either of the following conditions is true for a Windows XP-based computer, Windows incorrectly reports the number of physical processors:

•	The computer uses one or more hyperthreading-enabled processors.
•	The computer uses one or more multicore processors.

Note On a computer that is running Windows Vista, Windows correctly reports the number of physical processors.

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This issue occurs because Windows XP does not have the functionality to detect hyperthreading processors and multicore processors. This functionality was introduced in Windows Vista by using the Win32_ComputerSystem class and the Win32_Processor class in Windows Management Instrumentation (WMI).

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A hotfix is available to resolve this problem. After you apply this hotfix, the behavior of the Win32_ComputerSystem and Win32_Processor classes in Windows XP is the same as the behavior of these two classes in Windows Vista.

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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.

Prerequisites

To apply this hotfix, you must have Windows XP Service Pack 2 (SP2) installed on the computer.

Restart requirement

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

Hotfix replacement information

This hotfix does not replace any other previously released hotfixes.

Registry information

To use this hotfix, you do not have to make any changes to the registry.

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 XP with SP2, 32-bit version

File name	File version	File size	Date	Time	Platform	SP requirement
Cimwin32.dll	5.1.2600.3149	1,358,336	04-Jun-2007	04:01	x86	SP2
Kernel32.dll	5.1.2600.3149	986,112	04-Jun-2007	04:01	x86	SP2
Ntkrnlmp.exe	5.1.2600.3149	2,141,184	01-Jun-2007	11:18	x86	SP2
Ntkrnlpa.exe	5.1.2600.3149	2,062,208	01-Jun-2007	10:40	x86	SP2
Ntkrpamp.exe	5.1.2600.3149	2,020,864	01-Jun-2007	10:40	x86	SP2
Ntoskrnl.exe	5.1.2600.3149	2,185,472	01-Jun-2007	11:20	x86	SP2

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

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Before you apply this hotfix, the WMI classes and the WMI properties exhibit the following behavior.

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Win32_ComputerSystem

•	The NumberOfProcessors property returns the number of logical processors that are available on the system.
•	The NumberOfLogicalProcessors property is not available.

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Win32_Processor

•	The NumberOfLogicalProcessors property is not available.
•	The NumberOfCores property is not available.
•	The number of Win32_Processor instances that are returned is equal to the number of logical processors that are available on the system.

After you apply this hotfix, the WMI classes and the WMI properties exhibit the following behavior.

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Win32_ComputerSystem

•	The NumberOfProcessors property returns the number of physical processors that are available on the system.
•	The NumberOfLogicalProcessors property returns the number of logical processors that are available on the system.

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Win32_Processor

•	The number of NumberOfLogicalProcessors instances that are returned is equal to the number of logical processors that are available on the system.
•	The NumberOfCores property returns the number of cores that are available on the system.
•	The number of Win32_Processor instances that are returned is equal to the number of physical processors that are available on the system.

To determine whether hyperthreading is enabled for the processor, compare the value of the NumberOfCores property to the value of the NumberOfLogicalProcessors property. If hyperthreading is enabled in the basic input/output system (BIOS) for the processor, the value of the NumberOfCores property is less than the value of the NumberOfLogicalProcessors property.

For example, assume that a dual-processor system contains two processors that are each enabled for hyperthreading. This system can run four threads or four programs at the same time. In this case, the value of the NumberOfCores property is 2, and the value of the NumberOfLogicalProcessors property is 4.

For more information about the Win32_ComputerSystem class, visit the following Microsoft Web site:For more information about the Win32_Processor class, visit the following Microsoft Web site:For more information about these two classes in Windows Vista, visit the following articles in Microsoft Web site: For more information, click the following article number to view the article in the Microsoft Knowledge Base: For more information, click the following article number to view the article in the Microsoft Knowledge Base:

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