You may experience one of the following issues on a Windows Server 2008 system with the Hyper-V role installed or Microsoft Hyper-V Server 2008:
·         When you attempt to create or start a virtual machine, you receive one of the following errors:
·         The requested operation cannot be performed on a file with a user-mapped section open. (0x800704C8)
·         ‘VMName’ Microsoft Synthetic Ethernet Port (Instance ID
{7E0DA81A-A7B4-4DFD-869F-37002C36D816}): Failed to Power On with Error 'The specified network resource or device is no longer available.' (0x80070037).
·         The I/O operation has been aborted because of either a thread exit or an application request. (0x800703E3)
·         Virtual machines disappear from the Hyper-V Management Console

Cause

This issue can be caused by antivirus software that is installed in the parent p...

This issue can be caused by antivirus software that is installed in the parent partition and the real-time scanning component is configured to monitor the Hyper-V virtual machine files.

Resolution

To resolve this issue, configure the real-time scanning component within the ant...

To resolve this issue, configure the real-time scanning component within the antivirus software to exclude the following directories and files:
·         Default virtual machine configuration directory (C:\ProgramData\Microsoft\Windows\Hyper-V)
·         Custom virtual machine configuration directories
·         Default virtual hard disk directory (C:\Users\Public\Documents\Hyper-V\Virtual Hard Disks)
·         Custom virtual hard disk directories
·         Snapshot directories
·         Vmms.exe
·         Vmwp.exe
Notes:
·         If virtual machines are missing from the Hyper-V Management console, you must configure the antivirus exclusions, and then restart the Hyper-V Virtual Machine Management service.
·         If the error code was 0x800704C8, it is likely that the virtual machine configuration file was corrupted and the virtual machine may need to be re-created or restored from backup if restarting the Hyper-V Virtual Machine Management service does not resolve the issue.

Creating or starting a Hyper-V virtual machine on Windows Server 2008 or Microsoft Hyper-V Server 2008 may fail with error: 0x800704C8

http://support.microsoft.com/default.aspx?scid=kb;zh-tw;961804