The following link shows the list of software updates and hotfixes for Hyper-V in Windows Server 2008 / Windows Server 2008 R2. . These updates and hotfixes can help avoid some known issues and may save you a support call.

Comprehensive list of Hyper-V R2 updates/Hotfixes

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Comprehensive list of Hyper-V updates/Hotfixes

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Last Updated: May 26, 2010 / Posting on blog: July 28, 2010