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Assume that you have the Hyper-V server role installed on a computer that is running Windows Server 2008 R2. Additionally, you create a virtual machine that is running Windows 8 or Windows Server 2012 on the computer. In this situation, you experience one or more of the following issues:

  • The virtual machine stops responding.

  • You receive a Stop error message, and the computer restarts. This behavior stops all running virtual machines together with the computer.


The issue occurs because the Hypervisor does not handle the one-shot synthetic timer correctly.

Note The one-shot synthetic timer is also known as the aperiodic timer.


Update information

How to obtain this update

Microsoft Update

This update is available from the following Microsoft Update website:

Microsoft Download Center

The following files are available for download from the Microsoft Download Center:

Operating system


All supported x64-based versions of Windows Server 2008 R2

Download Download the update package now.

For more information about how to download Microsoft support files, click the following article number to view the article in the Microsoft Knowledge Base:

119591 How to obtain Microsoft support files from online services
Microsoft scanned this file for viruses. Microsoft used the most current virus-detection software that was available on the date that the file was posted. The file is stored on security-enhanced servers that help prevent any unauthorized changes to the file.


To apply this update, you must be running one of the following operation systems. Additionally, you must have the Hyper-V server role installed.

  • Windows Server 2008 R2

  • Windows Server 2008 R2 Service Pack 1 (SP1)

For more information about how to obtain a Windows 7 or Windows Server 2008 R2 service pack, click the following article number to view the article in the Microsoft Knowledge Base:


Information about Service Pack 1 for Windows 7 and for Windows Server 2008 R2

Registry information

To apply this update, you do not have to make any changes to the registry.

Restart requirement

You must restart the computer after you apply this update.

Update replacement information

This update replaces hotfix 2526776.


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

More Information

Because having a Windows Server 2012 guest on Windows Server 2008 Service Pack 2 (SP2) is not supported, the hotfix for Windows Server 2008 SP2 has been removed from this Microsoft Knowledge Base article. For more information about which guest operating systems are supported, go to the following Microsoft TechNet website:

About virtual machines and guest operating systemsFor more information about software update terminology, click the following article number to view the article in the Microsoft Knowledge Base:


Description of the standard terminology that is used to describe Microsoft software updates

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